Conceptual Questions: Physics 2 Final
What is the angle of refraction when a light ray is incident perpendicular to the boundary between two transparent materials?
0 degrees. When the ray of light is incident normally on the boundary between two materials, then the angle of incidence will become zero. sin theta (2) = n1/n2 x sin0 . sin theta (2) = 0, theta (2)= sin^-1 (0) = 0
Which is true as a block of ice melts?
1) Heat energy enters the ice/water system. Q is positive mL since you are going from a solid to liquor phase, adding heat rather than removing it. 2) Temperature of ice/water system remains constant since melting ice is an isothermal process. (Ice at 0 degrees is changed to water at 0 degrees)
Two linear waves have the same amplitude and speed, and otherwise are identical, except one has half the wavelength of the other. 1) Which transmits more energy? 2) By what factor?
1) The wave with the shorter wavelength 2) 4 If two waves have the same speed but one has half the wavelength of the other, the wave with the shorter wavelength must have twice the frequency of the other. The energy transmitted by a wave depends on the wave speed and the square of the frequency, The more oscillations, the more energy per time...if the wavelength is twice as big, frequency is 1/2, so the intensity is 1/4...if the wavelength is 1/2, the frequency is twice as big so the intensity is 4.
In an isothermal process, 2300 J of work is done by an ideal gas. 1)Is this enough information to tell how much heat has been added to the system? 2)If so, how much?
1) Yes 2) 2300 J In an isothermal process, the temperature remains constant making the change in internal energy 0 since a change in U relies on a change in temperature ( U = 3/2nRt). change in U(0) = Q - W, so Q = W, 2300 J = 2300 J
If one material has a higher density than another, must the molecules of the first be heavier than those of the second?
High density arises under 2 aspects: 1)Material particles have a greater mass occupying a specific volume 2)Material particles have a smaller mass, but are closely packed together, which makes a given amount of mass to occupy a smaller volume, and hence make the density higher. So, no - if one material has a higher density than another, the molecules of the first do not always have to be heavier than those of the second.
Adiabatic processes ...
Internal energy changes, there is no heat transfer in/out of the system
Is the image formed on the retina of the human eye upright or inverted?
The image formed own the retina is inverted because the eyes have a convex lens.
If the pressure in a gas is doubled while its volume is held constant, by what factor do vrms change?
The vrms increases by a factor of root 2. Vrms is directionally proportional to pressure (Squre root of 3xpressure / density), so when P is doubled, velocity gets multiplied by a factor of root 2.
If a string is vibrating as a standing wave in three segments, are there any places you could touch it with a knife blade without disturbing the motion?
Yes, positions in standing waves called nodes appear when no vibration takes place and in this instance the nodes occur when one segment ends and the other begins.
Can the amplitude of the standing waves be greater than the amplitude of the vibrations that cause them?
Yes, resonance...vibrating system or external force drives another system to oscillate with greater amplitude at a specific preferential frequency
Can you warm a kitchen in winter by leaving the oven door open?
Yes, the electrical energy emitted from the oven will be converted to heat energy in the heating coils.The heating coils warm the air in the oven and the warm air will warm the room. (2nd Law of thermodynamics - transfer hot to cold)
Does the focal length of a lens depend on the fluid in which it is immersed?
Yes. The focal length will change if the lens is immersed in a fluid. (1/f = (n-1)(1/r1 - 1/r2)
Relative to a stationary observer, a moving clock
always runs slower than normal. (time dilation)
The wavelengths corresponding to the harmonics of an organ pipe that is open at one end and closed at the other can be found by saying that the length of the pipe must be equal to
an odd number of quarter wavelengths. An organ pipe is considered a closed tube or system in which the fundamental frequency corresponds to a wavelength four times its length (1/4 wavelength = l)
The figure (Figure 1) shows various positions of a child on a swing moving toward a person on the ground who is blowing a whistle. At which position, A through E, will the child hear the highest frequency for the sound of the whistle?
C, The child is is moving with SHM, so the highest frequency is at the equilibrium position which is C. To have an increased pitch the relative motion of the source and the detector must be towards each other. The child would also hear the lowest frequency at C when swinging backwards.
Which of the following best explains why sweating is important to humans in maintaining suitable body temperature?
Evaporation of moisture from the skin extracts heat from the body, cooling the body down and preventing it from over heating. (homeostasis)
Pressure in a fluid decreases with depth. True or False?
False, pressure in a fluid increases with depth because there is an increase hydrostatic pressure.
To determine gauge pressure, add the atmospheric pressure to the absolute pressure. True or false?
False: Absolute (total) Pressure (P)= P0 (atmospheric pressure) + Gauge Pressure (PG) so to determine Gauge Pressure you must subtract the atmospheric pressure from the absolute pressure (P-P0) = PG)
If a person's face appears narrower through the glasses, is the person farsighted or nearsighted?
Nearsighted - diverging lenses are used to correct error, thicker at center, thinner at edges which perceives the face to appear narrower through the glasses.
When are the displacement and acceleration vectors in the same direction?
Never, a = -w^2x (-) indicates always in the opposite direction
Can a particle of nonzero mass attain the speed of light?
No, as the speed of the object increases, its inertial mass increases as well. As the speed of light is approached, the mass starts to increase very rapidly towards infinity. impossible to accelerate an object with non-zero mass to the speed of light
Can a light ray traveling in air be totally reflected when it strikes a smooth water surface if the incident angle is chosen correctly?
No, because the index of refraction is smaller than in the air then it is in the water. Thus, the light ray traveling in the air cannot be totally reflected from the surface. This total reflection is possible when the light ray must travel from a denser to rarer medium and not from a less to high denser medium.
If a wind is blowing, will this alter the frequency of the sound heard by a person at rest with respect to the source? Is the wavelength or the velocity changed?
No, f' = f (v+vo/v+vo), f' = f Both the wavelength and the velocity are changed (consider a large wave in slow motion as you can visualize how it would be stretched or compressed depending on what way the wind was blowing.) v= f x wavelength
Will potatoes cook faster if the water is boiling more vigorously?
No, one boiling point (100 degrees celsius). If water exceeds 100 degrees celsius it turns into steam which wastes input heat to cook the potatoes.
The units for the coefficients of expansion α are (C∘)^−1, and there is no mention of a length unit such as meters. Would the expansion coefficient change if we used feet or millimeters instead of meters?
No, we only need the ratio of the lengths to calculate α. Length contraction: change in length = original length x α x change in temperature, so α = (change in length) / (original length x the change in temperature) - units of length cancel each other so it wouldn't matter if you used any length unit and it would not change the coefficient of expansion.
Can you cool the kitchen on a hot summer day by leaving the refrigerator door open?
No, when the refrigerator is kept open in the kitchen, it will take heat from the room and deliver it back to the room. A fridge can be though of as a "heat pump". It takes air inside the fridge and cools it by removing heat from it. This heat has to go somewhere, though, and is usually blown out the back of the fridge by a little fan. (If you feel the back of a fridge on the outside it will usually be warm if the unit is running). For this reason, when a fridge is running it is really warming up the room a little bit. In fact, since we can't design a fridge to be perfectly efficient (the 2nd law of thermodynamics guarantees this), some of the electrical energy gets converted to heat, so more heat gets dumped outside the fridge than gets pumped out, so even if you open the fridge door to let the cool air escape the fridge will still be heating the room more than cooling it.
What about the focal length of a spherical mirror?
No. The focal length will not change if the spherical mirror is immersed in a fluid. (1/f = 1/d0 + 1/di) (Mirrors, spherical or otherwise, operate on the principle that the angle of reflection of a ray of light equals the angle at which it strikes the mirror's surface. That behavior is not affected by the medium in which the light travels, so the mirror's focal length would be no different in air or water. )
Consider what happens when you push both a pin and the blunt end of a pen against your skin with the same force. Decide what determines whether your skin is cut-the net force applied to it or the pressure.
Pressure- P = F/A, the net force applied remains the same If the area is large, the pressure is distributed over a large area and its effect is reduced The pen has more area so the force is distributed, thus the pin experiences more pressure from the net force and is more likely to cut your skin.
Which will give the greater improvement in the efficiency of a Carnot engine, a 10 C∘ increase in the high-temperature reservoir, or a 10 C∘ decrease in the low-temperature reservoir?
Since there is a larger range between the efficiency of a Carnot engine that decreases by 10 degrees celsius in the low-temperature reservoir, the efficiency increases more when the temperature of the cold reservoir decreases by some amount compared to an increase in a high-temperature reservoir. (ecold > ehigh)
For diffraction by a single slit, what is the effect of increasing the slit width?
The diffraction pattern would become more compact-wavelength is constant, as the width of the slit increases, theta min must decrease which causes the location of the first minimum to move closer from the central point, which causes the diffraction pattern to spread less. (sin(thetamin) = wavelength / d )
For diffraction by a single slit, what is the effect of increasing the wavelength?
The diffraction pattern would become spread out- width is constant, theta min must increase which causes the location of the first minimum to move farther from the central point causing the diffraction pattern to spread out.
For a simple harmonic oscillator, when (if ever) are the displacement and velocity vectors in the same direction?
The displacement and velocity vectors are in the same direction while the oscillator is moving away from its equilibrium position. v = wx
An engine manufacturer makes the claim that the engine they have developed will, on each cycle, take 100 J of heat out of boiling water at 100°C, do mechanical work of 80 J, and exhaust 20 J of heat at 10°C. What, if anything, is wrong with this claim?
The efficiency of this engine is greater than the ideal Carnot cycle efficiency, no real engine can have a greater efficiency than a Carnot (ideal) engine. (373 - 283)/ (373) = 24.12 % or 24.12 J > which would be the Carnot efficiency and the work, but efficiency of this engine is 80% (80 J = work / 100 J = Q input), which is greater than Carnot engine (24.12%)
What happens when a thin converging lens is moved closer to a nearby object?
The image moves farther from the lens since (focus to infinity) the lens is shifted towards the object from infinity to its focus. The image gets larger and magnified as the lens is shifted towards the object from infinity to its focus.
An object is placed along the principal axis of a spherical mirror. The magnification of the object is -3.0.
The negative sign indicates the image is real and inverted, as the image is real the mirror is concave because only concave mirror form real images and the image is on the same side of the object since the object is located along the principal axis.
Since the density of air decreases with an increase in temperature, but the bulk modulus B is nearly independent of temperature, how would you expect the speed of sound waves in air to vary with temperature?
The speed of sound in air should increase with increasing temperature. Speed of sound waves is inversely proportional to the square root of density. By increasing the temperature, the density of air decreases, which will lead to a larger range between the bulk modulus and density, leading to higher speed of sound.
A cup of water is scooped up from a swimming pool of water. Compare the temperature T and the internal energy U of the water, in both the cup and the swimming pool.
The temperature of both the water in the cup and in the pool would be the same because they are in the same surrounding hence the temperature would be changed simultaneously by the same surrounding. The internal energy would be greater in the swimming pool than in the cup because there are more molecules present in pool, resulting in a larger kinetic energy.
When both the pressure and the absolute temperature of an ideal gas are increased each by a factor of two, the volume occupied by the gas will?
The volume occupied by the gas will not change. The absolute temperature does not depend upon the properties of a particular material, it is directly proportional to kinetic energy.
For two beams of light traveling different distances in reaching a point, and to form maximum constructive interference at that point, the beams must travel paths that differ by a whole number of wavelengths. True or False
True, when a wave undergoes constructive interference it is in phase and the phase difference = m2pi. the beams travel paths that differ by a whole wavelength
When light travels from a larger index of refraction towards a smaller index of refraction, there is no phase change upon reflection at the boundary. True or False
True- if the light was traveling towards a larger index of refraction there would be a 180 degree phase shift
The projection of circular motion onto a straight line is simple harmonic motion. True or False?
True-Uniform circular motion describes the movement of an object traveling a circular path with constant speed. The one dimensional projection of this motion can be described as SHM.
At any depth in a fluid at rest, the pressure is the same in all directions at the given depth. True or False?
True-the pressure is isotropic, meaning the pressure is equally distributed in all directions when the fluid is a rest. (Also*Pascal's Law: A change in pressure at any point in an enclosed fluid at rest is transmitted undiminished to all points in the fluid.)
No device is possible whose sole effect is to transform a given amount of heat completely into work. True or false?
True: Kevin Planck statement of second law of thermodynamics - no heat engine can be 100% efficient - heat is a highly disorganized form of energy and all of it cannot be converted into useful work - some is converted to thermal / other energy
Which color of visible light would give the best resolution in a microscope?
Violet would produce the best resolution-shortest wavelength for visible light > the shorter the wavelength, the better the resolution
When a sound wave passes from air into water, do you expect the frequency or wavelength to change?
Wavelength, the frequency remains constant. If wave is traveling from a rarer to a dense medium than in order to travel faster in the denser medium it changes its wavelength. v = wavelength x f
Does the mirror equation, 1/d0+1/di=1/f, hold for a plane mirror?
Yes, a plane mirror is a flat mirror which is curved mirror with infinite focal lengths
If mass is a form of energy, does this mean that a spring has more mass when compressed than when relaxed?
Yes, a spring has more mass when compressed than when relaxed. A compressed string has more potential energy than a relaxed string.
Will any function of (x−vt)−see D(x,t)=D(x−vt)−represent a wave motion?
Yes, any function of (x-vt) will repent a wave motion because it will satisfy the wave equation. (x-vt, represents a wave going to the right, x+vt represent s a wave going to the left)
Does Huygens' principle apply to sound waves? To water waves?
Yes-Huygens' principle says that every point on a wavefront can be considered as a source of tiny wavelets moving with a the speed of the wave spread out in forward direction and tangent to these wavelets gives rise to a secondary wavefront. This causes the wave to moe in different directions instead of following a straight line path. Sound and water waves travel in all directions As the stone strikes the water surface the watering the vicinity moves upward.Every point on the primary wavefront then acts as tiny wavelets moving with a the speed of the wave spread out in forward direction whose tangent gives rise to a secondary wavefront
Suppose you are traveling in a spaceship at a velocity close to the speed of light. Which of the following would you notice?
You would notice no change in mass, pulse rate or height. any relativity changes are only observable to an external observer.
Relative to a stationary observer, a moving object
appears shorter than normal. (length contraction)
At a quiet pond with crystal clear water, you decide to fish with bow and arrow. When you aim at the fish you see, you must aim
deeper than you perceive the fish to be. real depth = apparent depth x index of water, apparent depth = real depth / index of water, meaning the fish appears shallower than it is
In a resonating pipe which is open at both ends, there
displacement antinodes at each end. Vibrating air in an open tube has displacement antinodes at both ends and has a fundamental frequency that corresponds to a wavelength twice its length, l = 1/2 wavelength
You are a passenger on a spaceship. As the speed of the spaceship increases, you would observe
nothing unusual about the length of your spaceship because you are the passenger on the space ship - any relativity changes are only observable to an external observer.
You are a passenger on a spaceship. As the speed of the spaceship increases, you would observe
nothing unusual about your watch. any relativity changes are only observable to an external observer.
Sunlight reflected from the surface of a lake
tends to be polarized with its electric field vector parallel to the surface of the lake. When light is reflected, the reflected light is completely polarized with its electric field vector parallel to the surface of the lake due to polarization (confining the components of electric field vector to a particular orientation and cutting the remaining orientations) When light incident on surface of lake, the electric field vector is perpendicular to the surface
Michelson and Morley concluded from the results of their experiment that
the experiment was a failure since there was no detectable shift in the interference pattern.
When a gas expands adiabatically...
the internal energy decreases. change in internal energy = -W (-pdv) since in adiabatic process has no heat exchange (Q=0)
The Michelson-Morley experiment was designed to measure
the velocity of the Earth relative to the ether=medium need to propagate
Two rays of light from the same source destructively interfere if their path lengths differ by how much?
wavelength(m + 1/2), where m is an integer. in destructive interference the phase difference is a half integral of wavelength
An ideal monatomic gas is allowed to expand slowly to twice its volume (1) isothermally; (2) adiabatically; (3) isobaric ally. 1)In which process is ΔEint the greatest? 2)In which process is ΔEint the least? 3)In which is W the greatest? 4)In which is W the least? 5) In which is Q the greatest? 6) In which is Q the least?
1) isobaric 2) adiabatic 3) isobaric 4) adiabatic 5) adiabatic 6) isobaric
Can real images be projected on the screen? Virtual?
A real image can be projected on the screen= In the formation of a real image, light rays converge at the point of location of the image. If a screen is placed in the position of the image, the real image can be projected on the screen but rays do not converge at the position of the image in the formation of a virtual image, so virtual images can not be projected on the screen.
A thermally isolated system consists of a hot piece of aluminum and a cold piece of copper. The aluminum and the copper are in thermal contact. The specific heat of aluminum is more than double that of copper. Which object experiences the greater amount of heat transfer during the time it takes the system to reach thermal equilibrium?
Both experience the same magnitude of heat transfer. From the principle of calorimetry, the heat energy gained by the colder object is equivalent to the heat energy lost by the hot body.
Consider two diffraction gratings with the same slit separation, the only difference being that one grating has 3 slits and the other 4 slits. If both gratings are illuminated with a beam of the same monochromatic light, make a statement concerning the separation between the orders.
Both gratings produce the same separation between orders, but the orders are better defined with the 4-slit grating. (peak width is inversely proportional to the number of lines in the grating, brighter and sharper orders for gratings with more slits)
Can real images be photographed? Virtual?
Both images can be photographed because they are visible to the eye.
Two spaceships are each traveling in a straight line at 0.95c. The first ship is moving directly toward the Sun. The second ship is moving directly away from the Sun. Observers on each ship measure the velocity of light coming from the Sun. What do they measure to be the velocity of the light coming from the Sun?
Both ships measure a velocity equal to c because the speed of light is the same in all frames based on the theory of relativity.
Suppose a gas expands to twice its original volume (a) adiabatically, (b) isothermally. Which process would result in a greater change in entropy?
Isothermally-there is no heat exchange in adiabatic processes so the change in entropy is 0.
What is wrong with the following statements? A fixed quantity of ideal gas at constant volume is warmed from a temperature of 20°C to 40°C. The pressure in the gas doubles during this process because the temperature doubles.
It is in Celsius not Kelvin, the appropriate temperature (in Kelvin) does not double in this process so the pressure does not double in this process.
Is it possible for the temperature of a system to remain constant even though heat flows into or out of it?
It is possible. Isothermal process is a change of a system in which the temperature remains constant. This occurs when a system is in contact with an outside thermal reservoir and the change will occur slowly enough to allow the system to continually adjust to the temperature of the reservoir through heat exchange. For example, melting ice or freezing water are isothermal processes. Heat flows into the ice melting it and out of the system when water becomes frozen both happening at 0 degrees.
A container is filled with a mixture of helium and oxygen gases. A thermometer in the container indicates that the temperature is 22°C. Which gas molecules have the greater average kinetic energy?
KE = 3/2KbT, both molecules have the same kinetic energy because the temperature is the same (kinetic energy is not dependent on the mass of the molecules)
What does special relativity reveal about the speed of light relative to its source?
Light moves at the same speed independent of the motion of the source according to the theory of relativity.
If system A is in equilibrium with system B, but B is not in equilibrium with system C, what can you say about the temperatures of A, B, and C?
System A and B have the same temperature since they are in equilibrium but since system B and C are not in equilibrium it must mean that C has a different temperature apart from system A and B.
If the pressure in a gas is doubled while its volume is held constant, by what factor do v¯ change?
The average velocity gets multiplied by a factor of root 2 as well.
A worker stands on top of a moving railroad car, and throws a heavy ball straight up (from his point of view). Ignoring air resistance, will the ball land back in his hand or behind him?
The ball will land back in his hand-law of universal gravitation- The railroad and ball had same horizontal velocity Vx during the complete flight in air, so they both cover the same distance in equal time and as a result you catch the ball. Had the bus accelerated or decelerated , the ball would have fallen somewhere else instead of your hand.
It is a well-known fact that water has a higher specific heat capacity than iron. Now, consider equal masses of water and iron that are initially in thermal equilibrium. The same amount of heat, 30 calories, is added to each. Which statement is true?
They are no longer in thermal equilibrium, the iron is warmer. Since iron has a lower specific heat than water: THEN Q = MCΔT M = mass of either water or iron hence M IS SAME Q = heat supplied is same then CΔT = CONSTANT Ci = SPECIFIC HEAT of iron Cw = SPECIFIC HEAT of water ΔTi = raise in temperature of iron ΔTw= raise in temperature of water given that Si < Sw then ΔTi > ΔTw thus iron will be warmer. ...basically since iron has a lower specific heat, it requires less heat to increase its temperature as compared to water with a high specific heat.
