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  • Physics Archive: Questions from 2024-01-1

    They will generally also be simultaneous to other observers who move relative to the first observer. They will always be separated in time to other observers whether they move relative to the first observer or not. They will generally not be simultaneous to other observers who move relative to the first observer.

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    Frame S’ passes frame S in the usual way (positive directions). A beam of light also travels in the positive direction. Which is true? The light's speed relative to S is less than its speed relative to S’. The light's speed relative to S is equal to its speed relative to S’. The light's speed relative to S is greater than its speed relative to S’.

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    Which is true about the detected frequency and wavelength of light that is emitted by a source that is moving toward the detector? The frequency and wavelength are both greater than the proper values, as measured on the source. The frequency and wavelength are both smaller than the proper values of the emitted light, as measured on the source. The frequency is greater than the proper frequency and the wavelength is smaller than the proper wavelength. The frequency is smaller than the proper frequency and the wavelength is greater than the proper wavelength.

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    An electron is within a one-dimensional, infinite potential well. Which is true about the integral of the probability density from one wall to the other? The value of the integral increases as we consider larger values of n. The value of the integral is the same for any value of n. The value of the integral decreases as we consider larger values of n.

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    In a Bohr-model hydrogen atom, what force holds the electron in orbit around the proton? a gravitational force that is radially inward, toward the proton a gravitational force that is radially outward, away from the proton an electric force that is radially outward, away from the proton an electric force that is radially inward, toward the proton

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    Which is true about the energy levels of hydrogen? Their spacing decreases as we move up through the levels. They are evenly spaced. Their spacing increases as we move up through the levels.

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    An electron and a proton have the same kinetic energy. Which has the greater de Broglie wavelength? Proton Electron

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    How does the shift in the x ray wavelength depend on the angle at which the x ray scatters? increases with an increase in angle stays the same with an increase in angle decreases with an increase in angle

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    Which is true about the Schrödinger equation? It applies to only relatively slow electrons (v << c). It applies to only relatively fast electrons (v ≈ c). It applies to electrons at any physically possible speed (v < c).

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    Stellar system Q1 moves away from us at a speed of 0.75c. Stellar system Q2, which lies in the same direction in space but is closer to us, moves away from us at a speed of 0.35c. What multiple of c gives the speed of Q2 as measured by an observer in the reference frame of Q1? 0.788 away from Earth 0.788 toward Earth 0.542 toward Earth 0.542 away from Earth

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    Light of frequency 9.6 × 1014 Hz is incident on a metal surface. The stopping potential for this metal at this frequency is 2.2 V. What is the cutoff frequency of this metal? 1. 5.1 × 1014 Hz 7.8 × 1014 Hz 8.5 × 1014 Hz 4.3 × 1014 Hz 9.6 × 1014 Hz

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    A meter stick flies past you, moving at a speed of 0.9c in direction parallel to its length. What length will you measure for the meter stick? More than 1.00 m. 1.00 m You will not be able to see the meter stick if it moves that fast. Less than 1.00 m.

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    Transforming the velocity of an object in one inertial reference frame (Frame A) to another (Frame B) requires knowing which of the following quantities? The acceleration of the object in both frames and its velocity in Frame A. The acceleration and velocity of the object in Frame A. The velocity of the object in Frame A and the velocity of Frame A relative to Frame B. The velocity of the object in Frame A and the distance between the two frames at the moment the velocity is measured.

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    The de Broglie wavelength of an electron with a kinetic energy of 4.355 eV is 0.110 nm. If the electron's energy doubles, the de Broglie wavelength will now be 0.156 nm 0.078 nm. 0.055 nm 0.110 nm.

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    A 100 m long ship lies at rest along the x axis. To whom does the ship appear longest? An observer moving at 0.5c in the -y direction. All of these observers measure the same length. An observer moving at 0.5c in the +y direction. An observer aboard the ship.

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    The stopping potential for electrons ejected by 7.7×1014 Hz electromagnetic radiation incident on a certain sample is 2.1 V. The kinetic energy of the most energetic electrons ejected and the work function of the sample, respectively, are 3.2 eV and 1.1 eV. 1.1 eV and 5.3 eV. 2.1 eV and 3.2 eV. 2.1 eV and 1.1 eV. 2.1 eV and 5.3 eV.

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    The ground state energy of an electron trapped in a 50.0 -pm wide infinite potential well is 150.8 eV. What is the width of an infinite potential well that traps an electron with a ground state energy of 452.4 eV? 50.0 pm 28.9 pm 16.7 pm 150.0 pm 86.6 pm

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    As the velocity of reference frame B relative to frame A approaches the speed of light, c, and the speed of an object in Frame B approaches c in the same direction, what value does the equation for relativistic velocity transformation indicate that the speed of the object relative to Frame A will approach? zero 2c Infinity c

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    You are impressed to see an alien spaceship fly past you at 0.920c of the speed of light. You measure the length of the ship to be 173 meters. What is the length of the ship as measured by those aboard it? meters

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    A box which has a length, L, along each side when measured in its rest frame moves in the x direction, parallel to one face of the box. How will the dimensions of the cube appear to an observer who watches the cube move past him? The length in the x direction will be L, but it will be shorter in the y and z directions. The lengths in the y and z directions will be L, but it will be longer than L in the x direction. The length in the x direction will be less than L but the lengths in the y and z directions will be greater than L. The lengths in the y and z directions will be L, but it will be shorter than L in the x direction.

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    Why do observers in different reference frames disagree about the length of an object? Because moving objects are stretched by forces which make them move. Because clocks in moving frames are less accurate than clocks at rest. Because moving objects get compressed to greater density by acceleration. Because they disagree about the time of events which define the ends of the object.

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    "Proper Length" is defined as the length of an object measured in a frame in which it is at rest. the ratio of an objects length in one frame to that in another. the length of an object measured in a frame in which it moves with constant positive velocity. the length of an object measured in a frame in which it moves with constant negative velocity.

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    If an observer sees a box moving down the z-axis at constant speed, which of the following observations about it are true? The length of the box in only the x direction is the same as if the box were at rest. The lengths of the box in the x and y directions are the same as if the box were at rest. The length of the box in only the z direction is the same as if it were at rest. The length of the box in only the y direction is the same as if the box were at rest.

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    If the kinetic energy of an electron moving within a potential energy well decreases, its de Broglie wavelength stays the same. increases. decreases.

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    The work function of lead is 4.14 eV. What is the cutoff frequency of lead? 1.00 × 1015 Hz 1.61 × 1014 Hz 4.14 × 1014 Hz 8.28 × 1014 Hz 3.21 × 1014 Hz

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    Length contraction is a direct consequence of which of the following? Orientation of axes in a non-inertial frame. Orientation of axes in an inertial frame. Conservation of momentum. Time dilation.

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    Stan sees a particle move with speed 0.749 c at an angle of 30.0 degrees to the x-axis. If Ollie moves away from Stan by moving along the x-axis at a speed of 0.217c, at what angle to the x-axis does Ollie see the particle move? degrees

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    The quantum number n associated with a trapped electron must be an integer value because: the associated electron is imaginary. it is impossible to determine the precise location of the electron. the associated electron is a matter wave. the associated electron is a particle.

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    A meter stick flies past you, moving in the direction of its length. You measure the length of the meter stick to be only 85.0 cm. How fast is the meter sick moving? State your answer as a fraction of the speed of light, c.

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    The stopping potential for electrons ejected by electromagnetic radiation incident on a certain sample is 1.5 V. The work function of the sample is 2.7 eV. What is the wavelength of the incident radiation? 830 nm None of the choices are correct. 300 nm 460 nm 7.1 × 107 m

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    The de Broglie wavelength of an electron with a kinetic energy of 2.553 eV is 0.476 nm. A second electron's de Broglie wavelength is 1.428 nm; its energy is therefore 0.851 eV. 2.553 eV. 22.977 eV 0.284 eV 7.659 eV

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    A ship flying away from Earth at 0.9c (where c is the speed of light) fires a missile which moves toward the Earth at a speed of 0.5c relative to the ship. How fast does the missile move relative to the Earth? 0.226c 0.727c 0.810c 0.500c

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    Light of frequency 9.6 × 1014 Hz is incident on a metal surface. The stopping potential for this metal at this frequency is 2.2 V. What is the cutoff wavelength of this metal? 700 nm 380 nm 310 nm 350 nm 590 nm

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    If an electron is currently in the third excited (n = 4) state, how many unique ways can it return to the ground state by emitting one or more photons? 1 4 2 3

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    A distant quasar is receding from the Earth at 0.900c (where c is the speed of light). The quasar emits a jet of charged particles directed away from the Earth at a speed of 6.08E+7 m/s relative to the quasar. How fast are the particles moving away from Earth, as measured by astronomers on Earth? m/s

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    A spaceship traveling directly away from Earth at 0.950 c (where c is the speed of light) fires a missile directly ahead. The missile moves away from the ship at 8.53E+7 m/s relative to the ship. What is the velocity of the missile relative to Earth? Define your coordinates so that positive velocities are directed away from Earth. m/s

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    A distant quasar is receding from the Earth at 0.900 c (where c is the speed of light). The quasar emits a jet of charged particles directed toward the Earth at a speed of 7.63E+7 m/s relative to the quasar and another jet ejected at equal speed directly away from Earth. What is the difference in the velocities of the two jets of particles relative to Earth? Define your coordinates so that positive velocities are directed away from Earth. m/s

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    A spaceship travelling directly away from Earth at 0.950c (where c is the speed of light) explodes and a piece of debris moves toward Earth at -271000000 m/s relative to the ship. What is the velocity of the debris relative to Earth? Define your coordinates so that positive velocities are directed away from Earth. m/s

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    A ship fires a projectile at a speed of 0.5c. What is the maximum speed another ship can have relative to the first and still be able to calculate the speed of the projectile using a Galilean transformation with no more than 1% error from the correct value for the velocity of the projectile? 0.5c 0.02c 0.2c 0.1c

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    A particle moves along the -x’ axis of frame S’ with speed 0.3c. Frame S’ moves with velocity 0.70c with respect to frame S. What is the velocity of the particle with respect to frame S? 0.51c c 0.83c 0.72c

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    The cutoff wavelength associated with a particular metal is 349 nm. What is the maximum kinetic energy of electrons emitted from a surface of this metal when illuminated by light of wavelength 237 nm? 112 eV 3.56 eV 8.81 eV 5.24 eV 1.68 eV

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    Pi mesons at rest have a half-life of T. If a beam of pi mesons is traveling at a speed of v = βc, the distance in which the intensity of the beam is halved is: cβT(1 – β^2) -1/2 cβT[(1 + β)/(1 - β)] 1/2 βvT (1 – β^2) 1/2vT none of the above

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    A rocket ship of rest length 100 m is moving at speed 0.8c past a timing device which records the time interval between the passage of the front and back ends of the ship. This time interval is: 0.20 µs 0.25 µs 0.33 µs 0.52 µs 0.69 µs

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    The length of a meter stick moving at 0.95c in 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: 0 s 1.1 × 10-9 s 3.2 × 10-9 s 3.5 × 10-9 s 1.1 × 10-8 s

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    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: 0.21c 0.50c 0.93c 1.3c 2.2c

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    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 0.90c away from Earth, passengers on board see: a dark lamp (the frequency is too high to be seen) a dark lamp (the frequency is too low to be seen) a red lamp a violet ramp a green lamp

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    The concentration of photons in a uniform light beam with a wavelength of 500 nm is 1.7 × 1013 m-3 . The intensity of the beam is: 6.8 × 10-6 W/m2 3.2 × 102 W/m2 1.0 × 103 W/m2 2.0 × 103 W/m2 4.0 × 103 W/m2

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    Electromagnetic radiation with a wavelength of 5.7 × 10-12 m is incident on stationary electrons. Radiation that has a wavelength of 6.6 × 10-12 m is detected at a scattering angle of: 10∘ 40∘ 50∘ 69∘ 111∘

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    Electromagnetic radiation with a wavelength of 3.5 × 10-12 m is scattered from stationary electrons, and photons that have been scattered through 50∘ are detected. After a scattering event the magnitude of the photon's momentum is: 0 kg⋅m/s 8.7 × 10-23 kg⋅m/s (1.5 1.10-22 kg⋅m/s 2.0 × 10-22 kg⋅m/s 2.2 × 10-22 kg⋅m/s

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    The wavelength of the matter wave associated with a 10-eV free electron is: 3.9 × 10-34 m 1.3 × 10-34 m 1.2 × 10-9 m 3.9 × 10-10 m 1.9 × 10-10 m

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    A stream of electrons, each with a kinetic energy of 450 eV, is sent through a potential-free region toward a potential barrier of "height" 500 eV and thickness 0.300 nm. The stream consists of 1 × 1015 electrons. How many should tunnel through the barrier? Pick the closest answer. The electron mass is 9.10938 × 10-31 kg. 3 × 103 1 × 106 4 × 105 9 × 105 7 × 104 6 × 104 7 × 106 8 × 107 4 × 107 8 × 109

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    The ground state energy of an electron in a one-dimensional trap with zero potential energy in the interior and infinite potential energy at the walls is 2.0 eV. If the width of the well is doubled, the ground state energy will be: 0.5 eV 1.0 eV 2.0 eV 4.0 eV 8.0 eV

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    An electron is trapped in a deep well with a width of 0.3 nm. If it is in the state with quantum number n = 3 its kinetic energy is: 6.0 × 10-28 J 1.8 × 10-27 J 6.7 × 10-19 J 2.0 × 10-18 J 6.0 × 10-18 J

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    An electron is trapped in an infinitely deep rectangular well with sides of length Lx = L and Ly = 2L. The energy of the state nx = 2, ny = 4 is: 8h^2/mL^2 h^2/mL^2 h^2/2mL^2 h^2/4mL^2 h^2/8mL^2

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    Under ideal conditions, a visual sensation can occur in the human visual system if light of wavelength 550 nm is absorbed by the eye's retina at a rate as low as 109 photons per second. What is the corresponding rate at which energy is absorbed by the retina? Number Units

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    The length of a spaceship is measured to be exactly 1/2 its rest length. (a) What is the speed parameter β of the spaceship relative to the observer's frame? (b) By what integer factor do the spaceship's clocks run slow, compared to clocks in the observer's frame? (a) Number Units (b) Number Units

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    The mass of a muon is 207 times the electron mass; the average lifetime of muons at rest is 2.25 μs. In a certain experiment, muons moving through a laboratory are measured to have an average lifetime of 7.02 μs. For the moving muons, what are (a) β (b) K, and (c) p ? The rest energy of the electron is 0.511MeV. (a) Number Units (b) Number Units (c) Number Units

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    A sodium lamp emits light at the power P = 150 W and at the wavelength λ = 550 nm, and the emission is uniformly in all directions. (a) At what rate are photons emitted by the lamp? (b) At what distance from the lamp will a totally absorbing screen absorb photons at the rate of 1.00 photon /cm2 s ? (c) What is the rate per square meter at which photons are intercepted by a screen at a distance of 2.30 m from the lamp? (a) Number Units (b) Number Units (c) Number Units

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    In a photoelectric experiment using a sodium surface, you find a stopping potential of 2.01 V for a wavelength of 290 nm and a stopping potential of 0.838 V for a wavelength of 399 nm. From these data find (a) a value for the Planck constant, (b) the work function Φ for sodium, and (c) the cutoff wavelength λ0 for sodium. (a) Number Units (b) Number Units (c) Number Units

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    An electron is trapped in a one-dimensional infinite potential well. For what (a) higher quantum number and (b) lower quantum number is the corresponding energy difference equal to 3 times the energy difference E76 between the levels n7 and n6 ? (c) Can a pair of adjacent levels have an energy difference equal to 2E76 ? (a) Number Units (b) Number Units (c)

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