|
The emission of light has most to do with the behavior of |
electrons |
|
The energy of a photon is directly proportional to its |
frequency |
|
Which of these will produce a continuous spectrum of colors |
a hot piece of wire |
|
electrons made to vibrate to and fro at a few hundred thousand hertz emit radio waves. |
visible light |
|
what does it mean to say an energy state is discrete |
the state has a precise energy |
|
in a neon tube, what occurs immediately after an atom is excited |
in de-excites and emits light. |
|
How does the difference in energy between energy levels relate to the energy of the photon that is emitted by a transition between those levels |
the energy of the photon is equal to the difference in energy between the energy levels |
|
How is the energy of a photon related to its vibrational frequency |
the energy is proportional to the frequency |
|
which has the higher frequency: red or blue light? which has the greater energy per photon: red or blue light? |
blue light, blue light |
|
what do the various colors displayed in the flame of a burning log indicate? |
the colors of the flames indicate the types of atoms that are emitting light in the flame |
|
how does an absorption spectrum differ in appearance from an emission spectrum? |
an emission spectrum consists of bright lines against a dark background, whereas an absorption spectrum consists of dark line against a bright rainbow background. |
|
distinguish between monochromatic light and sunlight |
sunlight has a wide range of frequencies and wavelengths, whereas monochromatic light has one wavelength and one frequency |
|
distinguish between coherent light and sunlight |
sunlight has a wide range of frequencies, wavelengths, and phases, whereas coherent light has one wavelength, one frequency, and one phase |
|
wave and a form of energy |
light is this and this |
|
light |
electromagnetic radiation= |
|
different wavelengths |
Color is changed by what? |
|
blue (towards) |
light with a shorter wavelength and higher frequency |
|
red (away) |
light with a longer wavelength and lower frequency |
|
positive |
proton= |
|
negative |
electron= |
|
neutral |
neutron= |
|
hydrogen |
stars are mostly |
|
its energy and color |
wavelengths tells us what |
|
light |
An electromagnetic wave (transverse wave) |
|
Inverse |
electric field and magnetic field |
|
Inverse |
Wavelength and color |
|
Inverse |
Wavelength and energy |
|
Direct |
Frequency and color |
|
Direct |
Frequency and energy |
|
Photon |
A "particle of light; oscillating, perpendicular electric and magnetic fields; ENERGY AT ITS PUREST |
|
A particle and a wave (wave for us); electric and magnetic |
A photon is both of these |
|
basically the same thing |
Photon and electromagnetic wave are |
|
Force Field |
The extension of a matter’s characteristics into open space |
|
Gravity |
A force |
|
Opposites attract, identicals repel |
Magnetic Characteristics: |
|
It’s its own energy |
Why does light not require its own medium? |
|
Shadow and space |
An absent of light |
|
An oscillating or accelerating electric charge |
What produces an electromagnetic wave? |
|
infrared light vibrates entire atoms and molecules and this vibration increases the temperature of the absorbing substance |
Why are infrared waves called heat waves? |
|
electrons |
The emission of light has most to do with the behavior of |
|
Radiowave |
Waves with long wavelengths and low frequencies, lowest energy ex: wifi |
|
there is no medium to slow it down |
Why is light the fastest thing possible? |
|
Transparent |
Objects that have the ability to transmit light through it |
|
Opaque |
Mediums that don’t let light transmit through |
|
Translucent |
In between transparent and opaque |
|
shorter wavelength |
hot= |
|
longer wavelength |
cold= |
|
Inverse |
Frequency and wavelength |
|
they have small wavelengths that can go between molecules |
Why can X-rays go through you? |
|
nuclear decay |
Gamma rays are only produced through this, otherwise they would be almost identical to X-rays |
|
nuclear fusion reactor |
The sun is what? |
|
Electricity |
Movement of electrons |
|
purple |
What color are black lights? |
|
Electromagnetic Wave |
A transverse wave created by electric and magnetic fields |
|
Microwaves |
lower than visible light, higher than radio waves, resonates water molecules |
|
X-rays |
Energy higher than visible light and ultraviolet light |
|
Gamma Rays |
Highest energy light, created through nuclear decay |
|
Pigment |
Color molecules; selectively reflects certain wavelengths of visible light which makes color |
|
Visible Light |
Transparent, translucent, opaque; ability to resonate other molecules |
|
color |
Frequency in light is |
|
brightness |
Amplitude in light is |
|
low energy to high energy and low frequency to high frequency |
ROYGBIV |
|
Sound is massless but it needs a mass to be heard |
Why can’t you hear in space? |
|
red, green, blue |
3 primary colors |
|
cyan |
green + blue |
|
magenta |
red + blue |
|
yellow |
green + red |
|
cyan, magenta, yellow |
3 secondary colors |
|
white |
Complimentary color |
|
red + green + blue, yellow + blue, cyan + red, magenta + green |
to make white |
|
it is reemitted |
What happens to light when it falls upon a material that has a natural frequency above or below the frequency of light? |
|
it is absorbed |
What happens to light when it falls upon a material that has a natural frequency equal to the frequency of light? |
|
A pigment selectively absorbs some frequencies of light and transmits others |
How does pigment affect light? |
|
Air molecules have resonance in the ultraviolet, so they scatter blue light more than red light; blue wavelengths are shorter and can’t pass through earth’s atmosphere so it scatters |
Why does the sky normally appear blue? |
|
the longer path length of sunlight and sunset scatters out more blue light |
Why does the sun look reddish at sunrise and sunset but not at noon? |
|
Orbitals |
Energy levels |
|
Absorption of Light |
When the wavelength of light matches the side of the object it is shining on, that object resonates (object+ electrons, atoms, molecules), the object vibrates and absorbs the energy = no more light |
|
water molecules |
microwaves resonate |
|
glass electrons and molecules |
ultraviolet and infrared light resonates |
|
air molecules |
ultraviolet also resonates |
|
their electrons vibrate to the oscillations of any incident light |
Metals are shiny because |
|
Polarized Lenses |
Can be translucent but when turned can be opaque |
|
direct |
Photon and energy |
|
What is the source of electromagnetic waves? |
Electrons |
|
What does it mean to say an energy state is discrete |
The state has a precise energy |
|
The energy of a photon is directly proportional to its _________. |
frequency |
|
If photon A has a higher energy than photon B, then it is also true that __________. |
photon A has a shorter wavelength and higher frequency than photon B |
|
How does the difference in energy between energy levels relate to the energy of the photon that is emitted by a transition between those levels? |
The energy of the photon is equal to the difference in energy between the energy levels. |
|
How is the energy of a photon related to its vibrational frequency? |
The energy is proportional to the frequency. |
|
Which has the higher frequency: red or blue light? Which has the greater energy per photon: red or blue light? |
Blue light, blue light |
|
Of the objects listed below, which emits the most infrared radiation? |
a star that is the same size as the Sun but is five times hotter |
|
You look at the emission line spectrum of a gas cloud and conclude that the cloud contains mostly hydrogen (H) and a little helium (He). How do you reach this conclusion? |
The emission lines due to H are stronger than those due to He. |
|
If an atom contained only four energy levels, how many possible different emission lines could it emit? |
6 |
|
How does the intensity at a given wavelength change if you increase the temperature? |
The intensity increases. |
|
How does the wavelength at which the maximum intensity occurs change when you increase the temperature? |
The wavelength decreases. |
|
How does the total energy per unit area emitted by the object change when you increase the temperature, and how do you know this from the graph provided? |
The total energy per unit area increases; we know this because the area under the graph increases when the temperature increases. |
|
How is the peak frequency of emitted light related to the absolute temperature of its incandescent source? |
The peak frequency is proportional to the absolute temperature. |
|
When a gas glows, discrete colors are emitted. When a solid glows, the colors are smudged. Why? |
Emitting electrons interact with nearby neighboring atoms in a solid. In a gas, there are few nearby atoms. |
|
The peak frequency of emitted radiation is directly proportional to _________. |
energy |
|
How does an absorption spectrum differ in appearance from an emission spectrum? |
An emission spectrum consists of bright lines against a dark background, whereas an absorption spectrum consists of dark lines against a bright rainbow background. |
|
Why is ultraviolet light, but not infrared light, effective in making certain materials fluoresce? |
The ultraviolet light photons have higher energy than visible light photons, whereas the infrared have lower energy. Thus, some of the ultraviolet energy can be reemitted as visible color. |
|
The difference between fluorescence and phosphorescence involves _________. |
time delay |
|
Distinguish between fluorescence and phosphorescence. |
Phosphorescence has a longer time delay between excitation and emission. |
|
Distinguish between the primary and secondary excitation processes that occur in a fluorescent lamp. |
Primary excitation is when electrons collide with and excite mercury gas. Secondary excitation is when ultraviolet light from the mercury excites a phosphor to emit visible light. |
|
A throbbing pulse of electromagnetic radiation is called a |
photon |
|
The energy of a photon depends on its |
frequency. |
|
The highest frequency of visible light is |
violet |
|
Which color of visible light carries the most energy per photon? |
violet |
|
Compared to the energy of a photon of red light, the energy of a photon of blue light is |
more |
|
An atom is excited when one or more of its electrons |
is boosted into higher energy levels. |
|
Light is emitted when an electron |
makes a transition to a lower energy level. |
|
An atom that absorbs a certain amount of energy can then emit |
a photon of the same or lower energy. |
|
The air that you breathe doesn’t emit visible light indicates that most of the electrons of its atoms are |
in the ground state. |
|
Green light emitted by excited mercury vapor corresponds to an energy transition in the mercury atom. A more energetic transition might emit |
blue light. |
|
Spectral lines take the shape of vertical lines because |
they are images of a vertical slit. |
|
Discrete spectral lines are observed when excitation occurs in a |
gas |
|
As a solid is gradually heated, it first glows |
red |
|
The radiation curve for a red hot fire-place poker peaks in the |
infrared region. |
|
The radiation curve for a blue hot star peaks in the |
ultraviolet region |
|
The hottest star is the one that glows |
blue |
|
If the radiation curve for an incandescent lamp filament peaks in the green region, the filament would appear |
white |
|
In the process of fluorescence, the input is high-frequency light and the output is |
lower-frequency light. |
|
A paint pigment that absorbs red light and gives off blue light |
doesn’t exist |
|
quantum # |
energy angle orientation |
|
Which are more successful in dislodging electrons form a metal surface: photons of violet light or photons of red light? Why? |
Violet light because the higher energy of a violet photon interacts with a single electron, and gives it enough energy to escape the metal |
|
What does it mean to say an energy state is discrete? |
The state has a precise energy |
|
How does the difference in energy between energy levels relate to the energy of the photon that is emitted by a transition between those levels? |
The energy of the photon is equal to the difference in energy between the energy levels. |
|
What is the uncertainty principle with respect to momentum and position? |
∆p∆x≥hbar |
|
What will produce a continuous spectrum of colors? |
A hot piece of wire |
|
What causes the spectrum of colors seen in gasoline splotches on a wet street? Why are these not seen on a dry street? |
Caused by interference of light waves reflected from the top of the gasoline layer and the bottom where the gasoline floats on water. The dry surface is rough and interference works best with a flat-topped layer of water. |
|
Why is argon, instead of air, used inside an incandescent bulb? |
Air contains oxygen that would react with and destroy the tungsten filament. Also, Argon is an inert gas. |
|
Will light pass through a pair of polaroids when the axes are aligned? When the axes are at right angles to each other? Why? |
The light that passes through the first Polaroid comes out completely polarized in the direction of that polarizer, so it easily passes through the analyzer with an aligned axis but not through one with an axis at right angles. |
|
Distinguish between coherent light and sunlight. |
Coherent light has one wavelength, frequency, and phase where as sunlight has a wide range of wavelengths, frequencies, and phases. |
|
A diffraction grating relies on light ____________. |
interference. |
|
When light undergoes interference, the quantity most affected is ___________. |
amplitude. |
|
What is a property of light waves but not of sound waves? |
Polarization. |
|
Polarization can occur when waves of light are |
aligned. |
|
Because of absorption, consider a Polaroid that transmits 40% of incident unpolarized light. Two such Polaroids, one atop the other, with their axes aligned, will transmit |
between 0% and 40%. |
|
Discrete spectral lines are clearly evident when excitation occurs in a |
gas. |
|
The proportion f ~ T tells us that the |
frequency of light emitted by a source is proportional to the temperature of the source. |
|
The dark lines in the solar spectrum represent light that is |
absorbed by the Sun’s atmosphere. |
|
Light from a fluorescent lamp is due to |
excitation. |
|
The ratio of a photon’s energy to its frequency is |
Planck’s constant. |
|
The kinetic energy of electrons ejected during the photoelectric effect depends on the |
frequency of illuminating light. |
|
The momentum of light is related to its |
wavelength. |
|
The wavelength of a matter wave is |
inversely proportional to its momentum. |
|
Distinguish between the shape of a converging lens and diverging lens. |
Converging= convex (thicker in the middle) Diverging= concave (thin in the middle) |
|
What happens as light goes through a convex lens? converging lens? |
convex= comes together to a point concave= spread out |
|
Where does no bending of light occur when it passes through a lens? |
in the middle |
|
Describe the orientation of a real image and virtual image compared to the original object viewed. |
real= upside-down (inverted) virtual= right-side up (upright) |
|
Which type of image can be projected onto a screen? |
real |
|
A. When does a converging lens magnify? |
A. When the object is between the focal point and the lens B. A virtual image, enlarged |
|
What conditions are necessary for a converging lens to form a real image? |
Object must be past the focal point HINT* When the object is: between f and 2f= enlarged at 2f= same size farther than 2f= small |
|
What condition must exist for a diverging lens to produce a real image? |
A diverging lens can NEVER produce a real image- only virtual images. |
|
What 3 sample rays are used for construction of a ray diagram? |
1. A line parallel to axis will pass through the focal point 2. A line through the center will pass straight through the lines without bending 3. A line through the focal point will bend and refract parallel to the axis |
|
How many rays are needed to locate an image? |
Two |
|
Compare the location of an object and image in relation to the lens: |
a. real image: object and image are on opposite sides of the lens b. virtual image: object and image are on the same side of the lens |
|
Name four common optical instruments other than eyeglasses |
Telescope, camera, projector, binoculars |
|
Describe the difference in focusing with a camera and how the eye focuses. |
Camera- focuses by moving the lens back and forth Eye- shape and thickness of the lens is changed by ciliary muscles= accomodation |
|
What kind of image forms on the back of your eye (and on the film of a camera)? |
real |
|
Compare the parts of the eye and the parts of a camera. |
shutter= eyelid diaphragm= iris aperture= pupil convex lens= convex lens film= retina |
|
*<b>Be able to label the parts of the eye</b>* |
… |
|
Transparent outer covering in front of the iris; light enters here and is refracted |
cornea |
|
Colored part of the eye; muscle that regulates the size of the pupil |
iris |
|
opening that lets light enter into the eye |
pupil |
|
convex; refracts light; changes shape to focus either close or far away |
lens |
|
light-sensitive layer of cells at the back of the eye. (rods- cells that we use for black and white vision; cones- cells that can see color) |
retina |
|
area on the retina; center of sharpest vision |
fovea |
|
area in front of the optic nerve where there are no rods or cones |
blind spot |
|
carries information from the eye to the brain |
optic nerve |
|
Explain the cause and correction of nearsightedness. |
cause- eyeball too long, image forms in front of retina correction- diverging lens will spread the light rays |
|
Explain the cause and correction for farsightedness. |
cause- eyeball too short, image forms behind the retina correction- converging lens will converge the light rays |
|
Explain the cause and correction for astigmatism. |
cause- abnormally shaped cornea correction- cylinder shaped lens |
|
An image that is formed by converging light rays and that can be displayed on a screen |
real image |
|
An image formed through reflection or refraction that can be seen by an observer but cannot be projected on a screen because light from the object does not actually come to a focus |
virtual image |
|
changing the shape and thickness of the lens by the action of the ciliary muscle |
accomodation |
|
a refractive error of the eye in which parallel rays of light from an external source do not converge on a single focal point on the retina. |
astigmatism |
|
What class of waves is emitted when electrons are made to vibrate to and fro at a few million billion hertz? |
Visible light wave |
|
What does it mean to say an energy state is discrete? |
Each element is also possesses its own characteristic pattern of electron shells, or energy states. These states are found only at certain energies; we say they are discrete |
|
Relative to the atomic nucleus, which has more potential energy, electrons in in inner electron shells or outer? |
Outer |
|
In a neon tube, what occurs immediately after an atom is excited? |
It drops back down to a lower energy level |
|
What is the relationship between the difference in energy between energy levels and the energy of the photon that is emitted by transition between those levels? |
the energy of the photon is equal to the difference in energy between energy levels |
|
How is the energy of a photon related to its vibrational frequency? |
The frequency of a photon is related to the energy transition of the jump. The frequency of a photon is directly proportional to its energy. |
|
Which has the higher frequency, red or blue light? which has the greater energy per photon, red or blue light? |
blue. blue. |
|
Can a neon atom in a glass tube be excited more than once? |
Yes, this process occurs many many times, as neon atoms continually undergo a cycle of excitation and de-excitation. |
|
What do the various colors displayed in the flame of a log represent? |
Different atoms in the flame emit colors characteristic of of their energy-level spacings. salt in a fire has a yellow tint because of sodium. |
|
Which puts out the greater percentage of its energy as a light, an incandescent lamp or a mercury-vapor lamp? |
Mercury-vapor |
|
What is a spectroscope, and what does it accomplish? |
An arrangement of slit, focusing lenses, and prism |
|
When gas slows, discrete colors are emitted. When a solid glows, the colors are smudged, why? |
electrons of outer orbits make transitions not only with the energy levels of their parent atoms but also between neighboring atoms. they bounce around over dimensions larger then a single atom, resulting in an infinite number of radiant-energy frequencies. |
|
How is peak frequency of emitted light related to the temperature of an incandescent source? |
peak frequency is directly proportional to the absolute temperature. |
|
how does an absorption spectrum differ in appearance from an emission spectrum? |
are like emission lines in reverse. |
|
What are fraunhofer lines? |
absorption lines |
|
How can astrophysicists tell if whether a star is receding or approaching earth? |
the frequency of light emitted by an approaching source is higher, receding, lower |
|
why is ultraviolet light, but not infrared, effective in making certain materials fluoresce? |
it needs a high frequency |
|
Which theory of light, the wave theory or particle theory, did the findings of Young, Maxwell, and Hertz support? |
wave theory |
|
Did Einstein’s photon explanation of the photoelectric effect support the wave theory or the particle theory of light? |
particle |
|
What exactly did Max planck consider quantized, the energy of vibrating atoms or the energy of light itself? |
energy of light itself |
|
What is a quantum of light called? |
photon |
|
In the formula E = hf, does f stand for wave frequency? |
frequency |
|
Which has a lower energy quanta – red light or blue light? X-rays or radio waves? |
red, radio |
|
Which are more successful in dislodging electrons from a metal surface, photons of violet or red light? |
violet |
|
Why wont a very bright beam of red light impart more energy to an ejected electron then a feeble beam of violet light. |
The brightness of the light does not effect the energy of ejected electrons. The number of photons in a light beam effects the brightness of the whole beam, whereas the frequency of light controls the energy of each individual photon |
|
Why do photographs in a book or magazine look grainy when magnified? |
When a photograph is taken with exceedingly feeble light, we find that the image is built up by individual photons that arrive independently and are seemingly random in their distribution. |
|
Does light behave primarily as a wave or primarily as a particle when it interacts with the crystals of matter in photographic film? |
particle |
|
Does light travel from one place to another in a wave or particle-like way? |
wave-like |
|
Does light interact with a detector in a wave-like or particle-like way? |
particle |
|
When does light behave as a wave, as a particle? |
A photon behaves as a particle when its being emitted by an atom or absorbed by photographic film or other detectors, and behaves like a wave in travelling from a source to the place where it is detected. |
|
What evidence can you cite for the wave nature of particles? |
? |
|
when electrons are diffracted through a double slit, do they hit the screen in a wavelike way or a particle-like way? is the pattern of hits wavelike or particle-like? |
particle wavelike pattern |
|
In which of the following are quantum uncertainties significant; measuring simultaneously the speed and location of a baseball; of a spitball; of an electron? |
electron |
|
What is the uncertainty principle with respect to momentum and position? |
558 |
|
If measurements show a precise position for an electron, can thos measurements show precise momentum also? |
No. Uncertainty principle pg 558 |
|
If measurement shows a precise value for energy radiated by an electron, can that measurement show a precise time for this event as well? |
No |
|
What is the distinction in this book between passively and actively observing an event? |
check pg 558 |
|
What is the principle of complementarity? |
… |
|
Which is more easily diffracted around buildings, AM or FM radio waves? Why? |
AM because they have longer wavelength |
|
What exactly did Thomas Young demonstrate in his famous experiment with light? |
Light passing through a double slit creates an interference pattern |
|
Why are interference colors primarily cyan, magenta, and yellow? |
Because one part of white light was cancelled to produce each |
|
Why will light pass through a pair of Polaroids when the axes are aligned but not when the axes are at right angles to each other? |
Because one will only pass vertical light waves and the other only horizontal light waves |
|
Why would depth not be perceived if you viewed duplicates of ordinary slides in a stereo viewer rather than the pairs of slides taken with a stereo camera? |
To see depth you need to see two different images of the object, each viewing it from a different angle |
|
How is this coherent light different from ordinary light? |
Coherent light has light waves in phases Normal light doesn’t |
|
What does it mean to say an energy state is discrete? |
It is one with a specific amount of energy |
|
What does it mean to say an atom is excited? |
An excited atom is one that has gained energy |
|
Which has the higher frequency red or blue light? Which has the greater energy per photon, red or blue light? |
Higher Frequency: Blue Greater Energy: Blue |
|
An electron loses some of its kinetic energy when it bombards a neon atom in a glass tube. What becomes of this energy? |
When an electron hits an atom, it transfers its energy to the atom when it turns it into light |
|
What pattern does every element have that enables each to emit its own characteristic colors of light? |
Emission spectra pattern |
|
How is the peak frequency of emitted light related to the temperature of its incandescent source? |
The peak light frequency emitted by a heated object is proportional to its temperature |
|
How can astrophysicists tell whether a star is receding or approaching Earth? |
Its light will be shifted to lower frequency red |
|
Why is ultraviolet light, but not infrared light, effective in making certain materials fluoresce? |
Because ultraviolet light has higher energy than infrared light |
|
What is responsible for the afterglow of phosphorescent materials? |
Phosphorescence causes an afterglow because some atom electrons remain in the higher energy orbit before falling back down and emitting light |
|
Distinguish between monochromatic light and coherent light. |
Monochromatic: light of one wavelength Coherent: light within phase waves |
|
Distinguish between the study of mechanics and the study of quantum mechanics. |
Mechanics: Study of motion Quantum Mechanics: Studies motion of electrons |
|
What is a quantum of light called? |
photons |
|
What evidence can you cite for the particle nature of light? |
The photoelectric effect shows light behaving as a particle |
|
When does light behave as a wave? When does it behave as a particle? |
Light behaves as a wave when it moves. Light behaves as a particle when it hits. |
|
What evidence can you cite for the wave nature of particles? |
Particles of matter are seen to act as waves when they create an interference pattern |
|
If you walk at 1 km/h down the aisle of a train that moves at 60 km/h, what is your speed relative to the ground? |
60 km/hr + 1km/hr = 61 km/hr |
|
Cite two examples of Einstein’s first postulate |
-Speed of light is constant -All laws of nature are the same in all frames of reference |
|
When a flashing light approaches you, each flash that reaches you has a shorter distance to travel. What effect does this have on how frequently you receive the flashes? |
You see the flashes more frequently at shorter intervals |
|
If you were traveling in a high-speed rocket ship, would metersticks on board appear to you to be contracted? |
The meterstick appears normal length. It is only when compared to one on earth that it would be shorter |
|
What would be the momentum of an object pushed to the speed of light? |
At light speed the momentum of an object is infinite |
|
Compare the amount of mass converted to energy in nuclear reactions and in chemical reactions |
Nuclear reactions release vastly more energy than chemical reactions |
|
What is the principal difference between the theory of special relativity and the theory of general relativity? |
General Theory of Relativity= Special Theory and Gravity |
|
In a spaceship accelerating at g, far from Earth’s gravity, how does the motion of a dropped ball compare with dropping one on Earth? |
A ball dropped in a spaceship accelerating up a 10 m/s ² looks the same as one pulled down by gravity |
|
What is the effect of strong gravitation on measurements of time? |
Strong gravity slows time |
|
In what kind of gravitational field are Newton’s laws valid? |
Earth’s gravity |
|
What occurs in the surrounding space when a massive object undergoes a change in its motion? |
A massive object bends spacetime |
|
What is a metastable state? |
Stable state with higher energy than the ground state energy, thermodynamically unfavourable but does exist. |
|
State the criteria for a thermodynamically stable state |
The Gibbs energy per mole/particle in state 1 is lower than in state 2 |
|
What is chemical potential? |
molar Gibbs energy – a measure of the potential of a substance to change state/phase μ = δG/δn |
|
What is the critical nucleus? |
The size of nuceli where energy no longer increases with size but begins to decrease |
|
Define the expression used to define critical nucleus size. How is it determined? |
R(c) = 2vγ/Δμ Droplet energy equation derived and set to zero (rate of energy change is zero at critical nucleus) |
|
State the expression used for the barrier to nucleation |
|
|
What value defines the barrier to nucleation |
free energy if the critical nucleus |
|
Show how the free energy barrier and critical nucleus change with chemical potential |
Barrier and critical nucleus size decrease as Δμ increases |
|
Why are nucleation rates higher in dirty systems rather than clean ones |
Presence of solid impurities allows adsorption of molecules onto the surface and lowers ΔG(c) |
|
Why do impurities lower the nucleation barrier? |
The impurity reduces the surface area of the droplet. |
|
What is crystallisation? |
expatial nucleation – when there is a specific match, orientated adsorption of the solute can occur which matches the crystal structure. |
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What kind of process is nucleation? |
Activated – need to get over an energy barrier to occur |
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What are crystals? |
Homogeneous solid comprised of a repeating 3D pattern of atoms, ions or molecules having fixed distances between the constituent parts |
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List some examples of crystals |
sodium chloride, bismuth, lysozyme (protein crystals are rare) |
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What steps are involved in crystal growth? |
1. Nucleation – formation of 3D nuclei 2. Growth – development of these nuclei into crystals |
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What is the driving force in crystal growth? |
supersaturation for both stages |
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What are the values of chemical potentials when a solution is in equilibrium? |
solid and solution chemical potentials are equal |
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What causes a crystal nuclei to continue to grow? |
If the flux of the material onto the curface exceeds the flux leaving the surface |
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What affects the rate of growth on a crystal surface? |
number/strength of interactions |
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Describe the mechanism of crystal growth |
growth units are free to migrate to favoured positions and growth occurs in a sequential manner |
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What affects the degree of interaction an crystal surfaces? |
underlying packing of atoms/ions in the crystal lattice as different surfaces have different surface energies |
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What does crystal growth resemble? |
the unit cell structure and the symmetry |
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Do crystals always look like the unit cell? |
not always |
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why do crystals grow? |
to achieve maximum intermolecular interactions |
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List the three types of crystal face |
flat (F) kinked (K) stepped (S) |
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What type of crystal face has the strongest interactions? Why? |
Kinked, interacts with a new crystal unit on 3 sides as oppose to two in a stepped surface or 1 on a flat surface K>S>F |
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How does number of sites relate to crystal growth? |
More sites = faster growth SLow growing surfaces dominate the crystal shape |
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Why are droplets of fluid spherical? |
Minimal surface area and keeps interfacial tension constant as liquid is isotropic (equal in all dimensions) |
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Why does direction matter in crystals where it doesn’t in liquids? |
Different crystal faces have different arrangements of atoms with different surface energies. A crystal wants to minimuse surafec energy so faces with largest surface energy will have the lowest area |
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What affects the final shape of crystal? |
The rates at which different faces grow |
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What is the origin of the two terms in the formula for droplet energy? |
Bulk term – arises due to chemical potential difference between the two phases Surface term – arises due to the surface energy of the interface |
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Reproduce a plot of the energy against droplet radius |
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Why is nucleation like a chemical reaction? |
Both a chemical reaction and nucleation are activated processes |
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How does the presence of impurities affect phase transitions? |
Impurities lower the free energy barrier to nucleation |
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Which is more easily diffracted around buildings, AM or FM radio waves? Why? |
AM because it has a longer wavelength |
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What exactly did Thomas Young demonstrate in his famous experiment with light? |
He demonstrated that light goes through a double slit creating an interference pattern |
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Why are interference color primarily cyan, magenta, and yellow? |
They are created by the destructive interference of one part of white light |
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Why will light pass through a pair of Polaroids when the axes are aligned but not when the axes are at right angles to each other? |
They are cancelled out |
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Why would depth not be perceived if you viewed duplicates of ordinary slides in a stereo viewer, rather than the pairs of slides taken with a stereo camera? |
To see in depth, you need two different pictures at two different angles |
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What does it mean to say an energy state is discrete? |
It has a specific amount of energy |
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What is the relationship between the difference in energy between energy levels and the energy of the photon that is emitted by a transition between those levels? |
The energy of the light is equal to the difference in the electron orbits energy level |
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What has the higher frequency, red or blue light? Which has the greater energy per photon, red or blue light? |
Blue = higher frequency Blue = higher energy |
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Can a neon atom in a glass tube be excited more than once? |
Yes by more incoming energy |
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What is a spectroscope, and what does it accomplish? |
It separates light into its individual frequency |
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How is the peak frequency of emitted light related to the temperature of its incandescent source? |
The peak frequency emitted by a heated object occurs at the highest temperature |
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How can astrophysicists tell whether a star is receding or approaching Earth? |
By receding, the light has a a red shift caused by the Doppler Effect |
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Why is ultraviolet light, but not infrared light, effective in making certain materials fluorescence? |
UV light causes minerals to fluorescence because of its energy |
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Distinguish between fluorescence and phosphorescence |
fluorescence= changing UV into visible light phosphorescence= glow in the dark-delay in emitting and absorbing light |
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Distinguish between monochromatic light and coherent light |
mono light= light of one wavelength coherent light= light waves in phase |
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What is a quantum of light called? |
photon |
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When does light behave as a wave? As a particle? |
behaves as a wave when light travels behaves as a particle when light hits |
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What evidence can you cite for the wave nature of particles? |
they behave as waves creating an interference pattern |
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Which are more successful in dislodging electrons from a metal surface- photons of violet light or photons of red light? |
Photons of violet light because of their higher energy |
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If you walk at 1 km/h down the aisle of a train that moves at 60 km/h, what is your speed relative to the ground? |
61 km/h |
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Cite two examples of Einstein’s first postulate |
ex1: ball falling at 9.8 m/s2 dropped by standing on ground or in an airplane going 500 mi/hr ex2: certain force will accelerate object no matter what speed |
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When a flashing light approaches you, each flash that reaches you has a shorter distance to travel. What effect does this have on how frequency you receive the flashes? |
There will be more flashes per second approaching you then a light not moving |
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If you were traveling in a high-speed rocket ship, would meter sticks on board appear to you to be shorter? |
It would appear normal unless compared to one on Earth |
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What would be the momentum of an object pushed to the speed of light? |
the object would have infinite momentum |
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Compare the amount of mass converted to energy in nuclear reactions and in chemical reactions |
nuclear reaction converts more mass into energy than chemical reactions |
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Do the relativity equations for time, length, and momentum hold try for everyday speeds? |
No they don’t work, use Newton’s Laws of Motion instead |
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What is the principal difference between the theory of special relativity and the theory of general relativity? |
general theory of relativity= special theory + gravity |
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In a spaceship accelerating at g, far from Earth’s gravity, how does the motion of a dropped ball coming with the motion of a ball dropped at Earth’s surface? |
the ball in the spaceship drops exactly the same on Earth acceleration= gravity |
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What is the effect of strong gravitation on measurements of time? |
strong gravity slows time |
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In what kind of gravitational field are Newton’s laws valid? |
Earth’s gravity field |
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What occurs in the surrounding space when a massive object undergoes a change in its motion? |
the object bends and warps space-time |
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Does Einstein’s theory of gravitation invalidate Newton’s theory go graviton? |
No it only explains gravity in a different way |
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Which is more easily diffracted around buildings, AM or FM radio waves? Why? |
AM b/c longer wavelength |
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What exactly did Thomas young demonstrate in his famous experiment with light? |
when light passes through a double-slit an interference pattern is created |
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Why are interference colors primarily cyan, magenta, and yellow? |
they’re created by the destructive interference of 1 part of white part |
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Why will light pass through a pair of Polaroid when axes are aligned but not when the axes are at right angels |
light doesn’t pass through polaroid’s at right angles because the vertical or horizontal light can only pass through a filter aligned the same way (ex. vertical light=>vertical filter & horizontal=>horizontal filter) |
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why would depth not be perceived if you viewed duplicates of ordinary slides in a stereo viewer, rather than the pairs of slides taken with a stereo camera? |
to be able to see depth, the object has to have been photographed from 2 different angles which gives 2 different images. |
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What does it mean to say an energy state is discrete? |
A discrete energy state has a specific amount of energy |
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what is the relationship b/w the difference in energy b/w energy levels and the energy of the photon that is emitted by a transition b/w those levels |
the energy of the light photon is equal to the difference in the electron orbits energy levels |
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what has a higher frequency, red or blue light? Which has the greater energy per photon red or blue light? |
blue light has a higher frequency blue light has a higher energy |
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can a neon atom in a glass tube be excited more than once? |
the neon atom can be excited over and over again by the incoming energy |
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what is a spectroscope, what does it accomplish |
spectroscope separates light into its individual frequency |
|
how is the peak frequency of emitted light related to the temperature of its incandescent source? |
the peak frequency emitted by a heated object occurs at the highest temperature |
|
how can astrophysicists tell whether a star is receding or approaching Earth? |
moving away– its light has a red shift (caused by the Doppler effect) |
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why is ultraviolet light but not infra-red light effective in making certain materials fluoresce |
UV light causes some minerals to fluoresce bc it has so much energy it can create RED+GREEN+green light |
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Distinguish b/w fluoresce and phosphorescence |
fluoresce– changing UV into invisible light phosphorescence– glow in the dark (delay b/w the atom absorbing emitting light) |
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Distinguish b/w monochromatic light and coherent light |
monochromatic– light of 1 wavelength coherent– light waves in phase |
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What is the principal difference b/w the theory of special relativity and the theory of general relativity? |
the general theory= the special theory+gravity |
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in a spaceship accelerating at g, far from earth’s gravity, how does the motion of a dropped ball compare with the motion of a ball dropped at earth’s surface? |
a ball drops in space ship accelerating up at g is exactly the same as on dropping on earth. acceleration=gravity |
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what is the effect of strong gravitation on measurements of time? |
strong gravity slows time |
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in what kind of gravitational field are newtons law valid |
in the Earth’s gravity field |
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What occurs in the surrounding space when a massive object undergoes a change in its motion? |
a massive object like a planet bends and warps space-time |
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Does Einstein’s theory of gravitation invalidate newton’s theory of gravitation? explain. |
Einstein’s theory of gravity(bend in space) doesn’t invalidate newton’s theory of gravity(force), it describes gravity in a different way |
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what is a quantum of light called? |
photon |
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when does light behave as a wave? as a particle? |
Light behaves as a wave when it moves. Light behaves as a particle when it hits. |
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What evidence can you cite for the wave nature of particles? |
polarization, thin film, interference, Newtons Rings? |
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When electrons are diffracted through a double-slit, do they hit a screen wavelike way or particlelike way? is this pattern of hits wavelike or particle-like? |
double-slit interference behaves as a wave |
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If you walk at 1 km/h down the aisle of a train that moves at 60 km/h what is your speed relative to the ground? |
speed of 61 km/h relative to the ground |
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cite two examples of Einstein’s first postulate |
-A ball will fall at the same speed, whether dropped on ground or in a moving plane -a certain force will accelerate an object by the same amount no matter what speed you do the experiment |
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when a flashing light approaches you, each flash that reaches you has a shorter distance to travel. what effect does this have on how frequently you receive the flashes? |
a flashing light that is approaching you will flash more frequently(more flashes/second) than a light that is not moving |
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if you were traveling in a high speed rocket ship, would metersticks on board appear to you to be contracted? explain. |
it would appear the same to some one on board it would appear shorter seen by someone on the earth |
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what would be the momentum of an object pushed to the speed of light? |
momentum would be infinite |
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compare the amount of mass converted to energy in nuclear reactions and in chemical reactions |
nuclear reaction convert much more mass into energy than chemical reaction |
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do the relativity equations for time, length, and momentum hold true for everyday speeds? explain. |
relativity equation doesn’t work for everyday speeds, use newton’s law of motion instead. |
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