Q&A Hero

Q: Rank following electromagnetic radiations according to the energies of their photons, from least to greatest. 1_ blue light 2_ yellow light 3_ xrays 4_ radio waves A) 1, 2, 3, 4 B) 4, 2, 1, 3 C) 4, 1, 2, 3 D) 3, 2, 1, 4 E) 3, 1, 2, 4

Q: Light beams A and B have the same intensity but the wavelength associated with beam A is longer than that associated with beam B. The photon flux (number crossing a unit area per unit time) is: A) greater for A than for B B) greater for B than for A C) the same for A and B D) greater for A than for B only if both have short wavelengths E) greater for B than for A only if both have short wavelengths

Q: The concentration of photons in a uniform light beam with a wavelength of 500 nm is 1.7 x1013m-3. The intensity of the beam is:A) 6.8x10-­6W/m2B) 3.2 x102W/m2C) 1.0 x103W/m2D) 2.0 x103W/m2E) 4.0 x103W/m2

Q: The intensity of a light beam with a wavelength of 500 nm is 2000 W/m2. The photon flux is about:A) 5 x1017/m2.sB) 5 x1019/m2.sC) 5 x1021/m2.sD) 5 x1023/m2.sE) 5 x1025/m2.s

Q: Which of the following electromagnetic radiations has photons with the greatest energy? A) blue light B) yellow light C) xrays D) radio waves E) microwaves

Q: The wavelength of light beam B is twice the wavelength of light beam B. The energy of a photon in beam A is: A) one-fourth the energy of a photon in beam B B) half the energy of photon in beam B C) equal to the energy of a photon in beam B D) twice energy of a photon in beam B E) four times the energy of a photon in beam B

Q: The frequency of light beam A is twice that of light beam B. The ratio EA/EBof photon energies is: A) 1/2 B) 1/4 C) 1 D) 2 E) 4

Q: The quantization of energy, E= nhf,is not important for an ordinary pendulum because: A) the formula applies only to mass-spring oscillators B) the allowed energy levels are too closely spaced C) the allowed energy levels are too widely spaced D) the formula applies only to atoms E) the value of hfor a pendulum is too large

Q: The units of the Planck constant hare those of: A) energy B) power C) momentum D) angular momentum E) frequency

Q: Two isotopes of hydrogen fuse to form a helium nucleus and a neutron:2H + 3H -> 4He + nThe masses are: 2H:2.013553 u3H:3.015501 u4He:4.001506 un:1.008665 uWhat is the Qvalue of this reaction?A) 1.9 MeVB) 2.5 MeVC) 2.8 MeVD) 17.6 MeVE) 938 MeV

Q: The work that must be done to increase the speed of an electron (m= 9.11 x10-31kg) from 0.90cto 0.95cis:A) 8.2 x10-13JB) 3.2 x10-13JC) 2.6 x10-13JD) 7.4 x10-14JE) 3.8 x10-15J

Q: A certain particle has a kinetic energy of 3.2 x10-10J and a momentum of 1.7 x10-18kg.m/s. Its mass is:A) 9.1x10-31kgB) 2.7 x10-27kgC) 4.5 x10-27kgD) 6.3 x10-27kgE) 8.6 x10-27kg

Q: An electron (m= 9.11 x10-31kg) has a momentum of 1.3x10-21kg .m/s. Its kinetic energy is:A) 6.3 x10-14JB) 8.2 x10-14JC) 1.5x10-13JD) 3.2x10-13JE) 4.0x10-13J

Q: The magnitude of the momentum of a particle can never exceed: A) mc, where mis its mass B) E/c, where Eis its energy C) K/c, where Kis its kinetic energy D) none of the above, but there is an upper limit E) none of the above; there is no upper limit

Q: If the kinetic energy of a particle is equal to its rest energy then its speed must be: A) 0.25c B) 0.50c C) 0.87c D) c E) unknown unless its mass is given

Q: The mass of a particle is m. In order for its total energy to be twice its rest energy, its momentum must be: A) mc/2 B) mc/ C) mc D) mc E) 2mc

Q: An electron (m= 9.11 x10-31kg) has a speed of 0.95c. Its kinetic energy is:A) 8.2 x10-14JB) 1.8 x10-13JC) 2.0 x10-13JD) 2.2 x10-13JE) 2.6 x10-13J

Q: The velocity of an electron is changed from c/2 in the "xdirection to c/2 in the +xdirection. As a result, its kinetic energy changes by: A) 2mc2 B) mc2 C) mc2 D) 0.5mc2 E) 0

Q: An electron is moving at 0.6c. If we calculate its kinetic energy using (1/2)mv2, we get a result which is: A) just right B) just half enough C) twice the correct value D) about 1% too low E) about 28% too low

Q: A particle with rest mass m moves with speed 0.6c. Its kinetic energy is: A) 0.18mc2 B) 0.22mc2 C) 0.25mc2 D) mc2 E) 1.25mc2

Q: If the kinetic energy of a free particle is much greater than its rest energy then its kinetic energy is proportional to: A) the magnitude of its momentum B) the square of the magnitude of its momentum C) the square root of the magnitude of its momentum D) the reciprocal of the magnitude of its momentum E) none of the above

Q: A particle with zero mass and energy Ecarries momentum: A) Ec B) Ec2 C) D) E/c E) E/c2

Q: According to relativity theory a particle of mass mwith a momentum of 2mchas a speed of: A) 4c B) 2c C) c D) 0.89c E) c/2

Q: An electron (m= 9.11 x10-31kg) has a speed of 0.95c. The magnitude of its momentum is:A) 2.6x10-22kg .m/sB) 2.9x10-22kg .m/sC) 6.0 x10-22kg .m/sD) 8.3 x10-22kg.m/sE) 8.8 x10-22kg .m/s

Q: If the kinetic energy of a free particle is much less than its rest energy then its kinetic energy is proportional to: A) the magnitude of its momentum B) the square of the magnitude of its momentum C) the square root of the magnitude of its momentum D) the reciprocal of the magnitude of its momentum E) none of the above

Q: According to the theory of relativity: A) mass is a form of energy B) moving particles lose mass C) momentum is not conserved in high speed collisions D) a rod moving rapidly sideways (perpendicular to its length) is shorter along its length E) a rod moving rapidly sideways (perpendicular to its length) is longer along its length

Q: If the mass of a particle is zero its speed must be: A) c B) infinite C) 0 D) any speed less than c E) any speed greater than c

Q: A distant star has a transverse speed (perpendicular to our line of sight) of 30,000 km/s with respect to Earth. Its spectrum has an absorption line at a frequency of 5.00 x 1014Hz. What is the frequency of that line as observed on Earth? A) 4.50 x 1014 Hz B) 4.90 x 1014 Hz C) 4.97 x 1014Hz D) 5.00 x 1014Hz E) 5.04 x 1014Hz

Q: A source at rest emits light of wavelength 500 nm. When it is moving at 0.90caway from an observer, the observer detects light of wavelength: A) 26 nm B) 115 nm C) 500 nm D) 2200 nm E) 9500 nm

Q: A source at rest emits light of wavelength 500 nm. When it is moving at 0.90ctoward an observer, the observer detects light of wavelength: A) 26 nm B) 115 nm C) 500 nm D) 2200 nm E) 9500 nm

Q: A spectral line of a certain star is observed to be "red shifted" from a wavelength of 500 nm to a wavelength of 1500 nm. Interpreting this as a Doppler effect, the speed of recession of this star is: A) 0.33c B) 0.50c C) 0.71c D) 0.80c E) c

Q: How fast should you move away from a 6.0 x1014Hz light source to observe waves with a frequency of 4.0 x1014Hz?A) 0.20cB) 0.39cC) 0.45cD) 0.51cE) 0.76c

Q: Visible light, with a frequency of 6.0 x1014Hz, is reflected from a spaceship moving directly away at a speed of 0.90c. The frequency of the reflected waves observed at the source is:A) 3.2 x1013HzB) 1.4 xï‚´1014HzC) 6.0 x1014HzD) 2.6 x1015HzE) 1.1 x1016Hz

Q: A console lamp in the cabin of a spaceship appears green when the ship and observer are both at rest. When the ship is moving at 0.90caway from Earth, passengers on board see: A) a dark lamp (the frequency is too high to be seen) B) a dark lamp (the frequency is too low to be seen) C) a red lamp D) a violet lamp E) a green lamp

Q: A train traveling very fast (v= 0.6c) has an engineer (E) at the front, a guard (G) at the rear and a passenger (S') exactly half way between them. Both E and G are equipped with yellow signaling lamps. The train passes a station, closely observed by the station master (S). Both E and G use their lamps to send signals. According to both S and S' these signals arrive simultaneously at the instant S' is passing S. According to S, the signal from E will look ______ and that from G will look _____: A) red, blue B) yellow, yellow C) blue, red D) blue, blue E) red, red

Q: Light from a stationary spaceship is observed, then the spaceship moves directly away from the observer at high speed. As a result, the light seen by the observer has: A) a higher frequency and a longer wavelength than before B) a lower frequency and a shorter wavelength than before C) a higher frequency and a shorter wavelength than before D) a lower frequency and a longer wavelength than before E) the same frequency and wavelength as before

Q: While emitting light of proper frequencyf0, a source moves to the right with speed c/4 relative to reference frame S. A detector, to the left of the source, measures the frequency to bef,which is greater thanf0. This means: A) the detector is moving to the right with a speed that is greater than c/4 relative to S B) the detector is moving to the right with a speed that is less than c/4 relative to S C) the detector is moving to the left with a speed that is greater than c/4 relative to S D) the detector is moving to the left with a speed that is less than c/4 relative to S E) the detector is not moving

Q: Light from some stars shows an apparent change in frequency because of: A) interference B) refraction by layers of air C) diffraction D) reflection E) relative motion

Q: Two electrons move in opposite directions at 0.70cas measured in the laboratory. The speed of one electron as measured from the other is: A) 0.35c B) 0.70c C) 0.94c D) 1.00c E) 1.40c

Q: Observer A measures the velocity of a rocket as and a comet as . Here and are parallel and in the direction of the observer's positive xaxis. The speed of the comet as measured by an observer on the rocket is:A) (u- v)/(1 - uv/c2)B) (u- v)/(1 - v2/c2)C) (u- v)/(1 - v2/c2)1/2D) (u- v)/(1 + uv/c2)E) (u+ v)/(1 - uv/c2)

Q: Star S1 is moving away from us at a speed of 0.8c. Star S2 is moving away from us in the opposite direction at a speed of 0.5c. The speed of S1 as measured by an observer on S2 is: A) 0.21c B) 0.50c C) 0.93c D) 1.3c E) 2.2c

Q: Frame S' moves in the positive xdirection at 0.6cwith respect to frame S. A particle moves in the positive xdirection at 0.4cas measured by an observer in S'. The speed of the particle as measured by an observer in S is: A) c/5 B) 5c/19 C) 8c/25 D) 25c/31 E) c

Q: Spaceship A, traveling past us at 0.7c, sends a message capsule to spaceship B, which is in front of A and is traveling in the same direction as A at 0.8crelative to us. The capsule travels at 0.95crelative to us. A clock that measures the proper time between the sending and receiving of the capsule travels: A) in the same direction as the spaceships at 0.7crelative to us B) in the opposite direction from the spaceships at 0.7crelative to us C) in the same direction as the spaceships at 0.8crelative to us D) in the same direction as the spaceships at 0.95crelative to us E) in the opposite direction from the spaceships at 0.95crelative to us

Q: Two flashes of light occur simultaneously at t= 0 in reference frame S, one at x= 0 and the other at x= 600 m. They are observed in reference frame S', which is moving at 0.95c in the positive xdirection. The origins of the two frames coincide at t= 0 and the clocks of S' are zeroed when the origins coincide. In S' the coordinate where the leading edges of the two light flashes meet and the time when they meet are:A) 300 m, 1.0 B) 15 m, 0.050C) 585 m, 1.95 D) 48 m, 0.16 E) 1900 m, 0.16

Q: An event occurs at x= 500 m, t= 0.90 in one frame of reference. Another frame is moving at 0.90cin the negative xdirection. The origins coincide at t= 0 and clocks in the second frame are zeroed when the origins coincide. The coordinate and time of the event in the second frame is:A) 500 m, 0.90 B) 1700 m, 5.5 C) 740 m, 2.4 D) 260 m, -0.60E) 590 m, -1.4

Q: An event occurs at x= 500 m, t= 0.90 in one frame of reference. Another frame is moving at 0.90cin the positive xdirection. The origins coincide at t= 0 and clocks in the second frame are zeroed when the origins coincide. The coordinate and time of the event in the second frame is:

Q: Relative to reference frame 1, reference frame 2 moves with speed vin the negative xdirection. When the origins of the two frames coincide the clocks in both frames are set to zero. An event occurs at coordinate x1and time t1as measured in reference frame 1 and at coordinate x2and time t2as measured in frame 2. If , then the coordinates and times of the event are related by:

Q: As a rocket ship moves by at 0.95ca mark is made on a stationary axis at the front end of the rocket and 9.0x10-8s later a mark is made on the axis at the back end. The marks are 100 m apart. The rest length of the rocket is:A) 31 mB) 78 mC) 100 mD) 240 mE) 320 m

Q: A rocket traveling with constant velocity makes an 8.4x1015m trip in 1 year. The proper time between events which mark the beginning and end of the trip is:A) 0.21 yearsB) 0.46 yearsC) 1.0 yearsD) 2.2 yearsE) 4.7 years

Q: Two events occur 100 m apart with an intervening time interval of 0.37 . The speed of a clock that measures the proper time between the events is:A) 0 cB) 0.45cC) 0.56cD) 0.90cE) 1.8c

Q: Two independent events occur 100 m apart with an intervening time interval of 0.42 . The proper time between the events is:

Q: Two events occur 100 m apart with an intervening time interval of 0.60 . The speed of a reference frame in which they occur at the same coordinate is:A) 0 cB) 0.25cC) 0.56cD) 1.1cE) 1.8c

Q: The length of a meter stick moving at 0.95cin the direction of its length with respect to the laboratory is measured by simultaneously marking its ends on an axis which is stationary in the laboratory. As measured by clocks moving with the stick, the time interval between the making of the back mark and the making of the front mark is:A) 0 sB) 1.1 x10-9sC) 3.2 x10-9sD) 3.5 x10-9sE) 1.1 x10-8s

Q: Which statement is correct? A) Galilean transformations are correct at any relative speed, but Lorentz transformations are only approximately correct for relative speeds near the speed of light. B) Lorentz transformations are correct at any relative speed, but Galilean transformations are only approximately correct for relative speeds near the speed of light. C) Galilean transformations are correct at any relative speed, but Lorentz transformations are only approximately correct for relative speeds that are small compared to the speed of light. D) Lorentz transformations are correct at any relative speed, but Galilean transformations are only approximately correct for relative speeds that are small compared to the speed of light. E) Galilean transformations are only approximately correct for relative speeds that are small compared to the speed of light, and Lorentz transformations are only approximately correct for relative speeds near the speed of light.

Q: Two events occur on the xaxis separated in time by tand in space by x. A reference frame, traveling at less than the speed of light, in which the two events occur at the same coordinate:

Q: Two events occur on the xaxis separated in time by t and in space by x. A reference frame, traveling at less than the speed of light, in which the two events occur at the same time:

Q: A clock is moving along the xaxis at 0.6c. It reads zero as it passes the origin (x= 0). When it passes the x= 180 m mark on the xaxis the clock reads:

Q: A certain automobile is 6.0 m long if at rest. If it is measured to be 4.8 m long while moving, its speed is: A) 0.1c B) 0.3c C) 0.6c D) 0.8c E) > 0.95c

Q: A rocket ship of rest length 100 m is moving at speed 0.8cpast a timing device which records the time interval between the passage of the front and back ends of the ship. This time interval is:

Q: A meter stick moves in the direction of its length through a laboratory. According to measurements taken in the laboratory, its length is 0.31 m. The speed of the meter stick relative to the laboratory is: A) 0.096c B) 0.31c C) 0.69c D) 0.83c E) 0.95c

Q: A consequence of Einstein's theory of relativity is: A) moving clocks appear to run faster than when they are at rest B) moving rods appear shorter than when they are at rest C) light has both wave and particle properties D) the laws of physics must appear the same to all observers moving with uniform velocity relative to each other E) everything is relative

Q: A measurement of the length of an object that is moving relative to the laboratory consists of noting the coordinates of the front and back: A) at different times according to clocks at rest in the laboratory B) at the same time according to clocks that move with the object C) at the same time according to clocks at rest in the laboratory D) at the same time according to clocks at rest with respect to the fixed stars E) none of the above

Q: According to the theory of relativity: A) moving clocks run fast B) energy is not conserved in high speed collisions C) the speed of light must be measured relative to the ether D) momentum is not conserved in high speed collisions E) none of the above

Q: A consequence of Einstein's theory of relativity is: A) moving clocks appear to run more slowly than when they are at rest B) moving rods appear longer than when they are at rest C) light has both wave and particle properties D) the laws of physics must appear the same to all observers moving with uniform velocity relative to each other E) everything is relative

Q: A meter stick moves sideways (that is, in a direction perpendicular to its length) at 0.95c. According to measurements taken in the laboratory, its length is: A) 0 m B) 0.098 m C) 0.31 m D) 1.0 m E) 3.2 m

Q: A meson moving through a laboratory of length xat a speed vdecays after a lifetime T as measured by an observer at rest in the laboratory. If the meson were at rest in the laboratory its lifetime would be:

Q: Pi mesons at rest have a half-life of T.If a beam of pi mesons is traveling at a speed of, the distance in which the intensity of the beam is halved is:

Q: A meson when at rest decays 2 after it is created. If moving in the laboratory at 0.99c, its lifetime according to laboratory clocks would be:A) the sameB) 0.28 C) 4.6 D) 14 E) none of these

Q: An observer notices that a moving clock runs slow by a factor of exactly 10. The speed of the clock is: A) 0.0100c B) 0.100c C) 0.900c D) 0.990c E) 0.995c

Q: A millionairess was told in 1992 that she had exactly 15 years to live. However, if she immediately takes off, travels away from the Earth at 0.8 cand then returns at the same speed, the last New Year's Day the doctors expect her to celebrate is: A) 2001 B) 2003 C) 2007 D) 2017 E) 2033

Q: As we watch, a spaceship passes us in time t. The crew of the spaceship measures the passage time and finds it to be t'. Which of the following statements is true?A) tis the proper time for the passage and it is smaller than t'B) tis the proper time for the passage and it is greater than t'C) t' is the proper time for the passage and it is smaller than tD) t' is the proper time for the passage and it is greater than tE) None of the above statements are true.

Q: The spaceship U.S.S. Enterprise, traveling through the galaxy, sends out a smaller explorer craft that travels to a nearby planet and signals its findings back. The proper time for the trip to the planet is measured by clocks: A) on board the Enterprise B) on board the explorer craft C) on Earth D) at the center of the galaxy E) none of the above

Q: The proper time between two events is measured by clocks at rest in a reference frame in which the two events: A) occur at the same time B) occur at the same coordinates C) are separated by the distance a light signal can travel during the time interval D) occur on the Earth's surface E) none of the above

Q: Two events occur simultaneously on the xaxis of reference frame S,one at x = -­aand the other at x = +a. According to an observer moving in the positive xdirection:A) the event at x = +a occurs firstB) the event atx = -aoccurs firstC) either event might occur first, depending on the value of aand the observer's speedD) the events are simultaneousE) none of the above

Q: The speed of light in vacuum is approximately A) 186,000 miles per hour B) 300,000 km per minute C) one foot per nanosecond D) 186,000 feet per second E) 300,000 meters per second

Q: A basic postulate of Einstein's theory of relativity is: A) moving clocks run more slowly than when they are at rest B) moving rods are shorter than when they are at rest C) light has both wave and particle properties D) the laws of physics must be the same for observers moving with uniform velocity relative to each other E) everything is relative

Q: A train traveling very fast (v= 0.6c) has an engineer (E) at the front, a guard (G) at the rear and an observer (S') exactly half way between them. Both E and G are equipped with yellow signaling lamps. The train passes a station, closely observed by the station master (S). Both E and G use their lamps to send signals. According to both S and S' these signals arrive simultaneously at the instant S' is passing S. According to S': A) E and G sent their signals simultaneously from different distances B) G sent his signal before E and from further away C) G sent his signal before E but was the same distance away D) E sent his signal before G and from further away E) none of the above

Q: Two events occur simultaneously at separated points on the yaxis of reference frame S. According to an observer moving in the positive xdirection: A) the event with the greater ycoordinate occurs first B) the event with the greater ycoordinate occurs last C) either event might occur first, depending on the observer's speed D) the events are simultaneous E) none of the above

Q: Light of wavelength is normally incident on some plane optical device. The intensity pattern shown is observed on a distant screen ( is the angle measured to the normal of the device). The device could be:A) a single slit of width WB) a single slit of width 2WC) two narrow slits with separation WD) two narrow slits with separation 2WE) a diffraction grating with slit separation W

Q: For a certain multiple-slit barrier the slit separation is 4 times the slit width. For this system: A) the orders of the lines that appear are all multiples of 4 B) the orders of the lines that appear are all multiples of 2 C) the orders of the missing lines are all multiples of 4 D) the orders of the missing lines are all multiples of 2 E) none of the above are true