Physics 221 Final Exam Practice (both forms)

(R13-7) X-ray of wavelength 1.5 angstrom reflects off electrons at 90 degrees. How much momentum is transferred to the electrons?

5.8 x 10^-26 kg * m/s

(R13-2) Visible light sines on the metal surface of a photocell having a work function of 1.30 eV. The maximum kinetic energy of the electrons leaving the surface is 0.92 eV. Determine the lights wavelength

560 nm

(R10-6) Unpolarized light of intensity I_0 passes through a polarizer whose polarization axis is 30 degrees with respect to vertical polarization. What is the intensity of transmitted light? A. I_0 B. I_0/2 C. I_0/4 D. I_0 cos^2(30) E. I_0 sin^2(30)

B

(R12-6) A person stands on the ground watching cars zoom past on a straight racetrack. When she measures the length of the moving cars she measures: A. the proper length of the cars B. a length shorter than the proper length C. a length longer than the proper length

B

(R13-3) If red light incident on a metal causes an electron with some KE to be emitted, higher intensity red light will: A. produce electrons with higher KE B. produce mroe electrons with same KE C. neither A nor B

B

(R14-1) What is the wavelength of the line in the hydrogen spectrum that is comprised of transition from n = 5 to n = 3 levels? A. 1880 nm B. 1280 nm C. 2250 nm D. 1920 nm

B

(R14-2) How many electrons can occupy 4f subshell? A. 4 B. 14 C. 16 D. 32

B

(R14-5) The more accurately we know the velocity of a particle, the less accurately we can know its: A. mass B. position C. speed D. all of the above

B

(R15-1) Neglecting recoil of the gold nucleus, how much kinetic energy must an alpha particle (charge 2 x 10^-19 C) have to approach to within 1.95 x 10^-14 m of a gold (Au79) nucleus? A. 14.6 MeV B. 11.7 MeV C. 18.2 MeV D. 22.7 MeV

B

(R15-4) Which of the following is NOT a fundamental interaction? A. gravitation B. frction C. strong D. weak

B

(R15-5) Tritium has a half-life of 12.3 years. How many years will elapse when the radioactivity of a tritium sample diminishes to 30% of its original value? A. 10.6 years B. 21.4 years C. 24.6 years D. 35.6 years

B

(R15-6) What is the electric force on an electron in a hydrogen atom in ground state? (r_1 = 0.35 x 10^-10 m) A. 4.3 x 10^-18 N B. 8.2 x 10^-8 N C. 27.2 N D. 5.2 x 10^11 N

B

(R15-8) An object is placed in front of a lens at 20 cm and the image is formed at 15 cm from the lens on the same side of the object. What lens is being used? A. concave, f = 0.16 cm B. concave, f = 60 cm C. convex, f = 0.16 cm D. convex, f = 60 cm

B

(R8-6) The image produced by a plane mirror: A. is real because refracted light hits the image B. is virtual because no light actually leaves the image C. appears to be in front of the mirror D. appears to be half the size of the object

B

(R9-7) An object is placed exactly at the focal length of a lens (f = -10 cm). Where will the image be formed? A. no image will be produced B. the image will be at f/2 C. the image will be at the focal point D. the image will be at 2f

B

(R14-3) Starting from rest, an electron accelerates through a potential difference of 67 V. What is its de Broglie wavelength?

1.5 x 10^-10 m

(R13-4) A powerful 0.50 W laser emitting 670 nm photons shine on the sail of a tiny 800g satellite. Determine the forc eon the sail if the light is totally reflected

3.3 x 10^-9 N

(10B Reference the exam for diagram) Consider an LC circuit with L = 13 mH and C = 2295 pF (1 picofarad = 10^-12 F). At what frequency is the reactance of the inductor equal to the reactance of the capacitor? What is the resonant frequency of the circuit? A. 29134 Hz; 29134 Hz B. 58268 Hz; 29134 Hz C. 58268 Hz; 16821 Hz D. 29134 Hz; 58268 Hz B. 58268 Hz; 58268 Hz

A

(11C) An electromagnetic wave travels in free space in the +y direction, as shown in the figure. If the electric field at the origin is along the +z direction, what is the direction of the magnetic field? A. +x B. -x C. -z D. +z E. +y

A

(13A) Einstein's theory of relativity is based in part on which one of the following postulates? A. speed of light in a vacuum is same for all observes regardless of source velocity B. energy is conserved only in elastic collisions C. space and time are absolutes D. mass and energy are equivalent E. both C and D

A

(15B) The camera on a spy satellite has a lens with a diameter of 3.1 m. This satellite is in low-Earth orbit about 2.9 x 10^5 m above the surface of the Earth. What is the approximate size of the smallest feature the camera can resolve when taking a picture of something on the Earth's surface? Assume blue light with a wavelength of 400 nm. Ignore the effect of the Earth's atmosphere on the resolution. A. 4.5 cm B. 6.2 cm C. 26 cm D. 6.7 cm E. 13.7 cm

A

(18A) The quantum mechanical model of the hydrogen atom suggests a visual picture of the electron as which of the following? A. planetary orbiting body B. probability cloud C. raisin in pudding D. light quantum E. photon

A

(1A) The electric field at the surface of a positively charged conductor has a direction characterized by which of the following? A. perpendicular outward and away from the charge B. at a 45 degree angle to the surface C. tangent to the surface D. perpendicular inward toward the charge E. a cylindrical surface with the wire at the center

A

(1C) The figure shows part of the energy level diagram of a certain atom. The energy spacing between levels 1 and 2 is twice that between 2 and 3. If an electron makes a transition from level 3 to level 2, the radiation of wavelength (lambda) is emitted. What possible radiation wavelengths might be produced by other transitions between the three energy levels? A. both lambda/2 and lambda/3 B. only lambda/2 C. only 2*lambda D. both 2*lambda and 3*lambda

A

(28A) A 6.0 mC charge is placed at the origin and a second charge is placed on the x axis at x = 0.3 m. If the resulting force on the second charge is 5.4 N in the positive x direction, what is the value of its charge? A. 9.0 nC B. -9.0 nC C. 9.0 uC D. -9.0 uC E. 9.0 C

A

(29A) If a light bulb has half the resistance of a 50 W light bulb, what would be its wattage? Assume both bulbs are attached to a 120 V circuit. A. 100 W B. 25 W C. 200 W D. 50 W E. need more information

A

(2A) Decreasing the voltage across the two plates of a capacitor will produce what effect on the capacitor? A. decrease charge B. increase capacitance C. decrease capacitance D. increase charge E. both B and C

A

(32A) What is the impedance of an AC series circuit that is constructed of a 10.0 ohm resistor along with 24.0 ohm inductive reactance and 7.0 ohm capacitive reactance? A. 19.7 ohms B. 11.2 ohms C. 41.0 ohms D. 27.7 ohms E. 3.5 ohms

A

(35A) A binary star system in the constellation Orion has an angular separation between the stars of 10^-5 radians. Assuming a wavelength of 700 nm, what is the smallest aperture (diameter) telescope that will just resolve the two stars? A. 8.5 cm B. 4.2 cm C. 6.1 cm D. 3.0 cm E. 0.9 cm

A

(6A) According to Lenz's law the direction of an induced current in a conductor will be that which tends to produce which of the following effects? A. oppose the effect which produces it B. enhance the effect which produces it C. produce the greatest voltage D. produce a greater heating effect E. both B and C

A

(6B) The flux through an inductor with L = 4.59 mH changes at a rate of delta_Phi/delta_t = 0.0043 T*(m^2/s). What is the rate of change delta_I /delta_t of the current through the inductor? A. 0.937 A/s B. 0.656 A/s C. 0 D. 1.405 A/s E. 1.78 A/s

A

(7B) The distance between atoms in a crystal of NaCl is 0.25 nm. The crystal is being studied in a neutron diffraction experiment. At what speed must the neutrons be moving so that their de Broglie wavelength is 0.25 nm? A. 1582 m/s B. 2848 m/s C. 2373 m/s D. 1098 m/s E. 3332 m/s

A

(8B) A surgeon is attempting to correct a detached retina by using a pulsed laser. (a) if the pulses last for 30 ms and if the output power of the laser is 0.5 W, how much energy is in each pulse? (b) if the wavelength of the laser light is 648 nm, how many photons are present in each pulse? A. 15 mJ, 4.89 x 10^16 photons B. 30 mJ, 4.89 x 10^15 photons C. 30 mJ, 9.78 x 10^16 photons D. 48 mJ, 9.78 x 10^15 photon E. 15 mJ, 9.78 x 10^15 photons

A

(9A) A radio wave signal, which transmits at a frequency of 10.4 MHz, has what wavelength? A. 28.8 m B. 2.4 x 10^-2 m C. 4.17 m D. 41.7 m E. 2.88 x 10^7 m

A

(R13-8) What is the energy of a photon from red light (630 nm) ? A. 1.97 eV B. 3.15 eV C. 3.94 eV D. 12.0 eV

A

(R14-8) The energy of an atom in the Bohr model is proportional to: A. 1/n^2 B. 1/n C. n D. n^2

A

(10A) A light ray in air enters and passes through a block of glass. What can be stated with regard to its speed after it emerges from the block back into air? A. speed is less than when in glass B. speed is same as that before it entered glass C. speed is same as that in glass D. speed is less than before it entered glass E. depends on the index of refraction of the particular glass

B

(12A) According to a postulate of Einstein, which of the following describes the nature of the laws of physics as one observes processes taking place in various inertial frames of reference? A. laws are the same only in inertial frames moving at near speed of light B. laws are the same in all inertial frames C. laws are the same only in inertial frames with zero velocity D. laws are the same only in inertial frames moving at low velocities E. laws are the same only in absolute inertial frames

B

(13C) If a proton and an electron have the same de Broglie wavelengths, which one is moving faster? A. the electron B. the proton C. they both have the same speed

B

(14B Reference the exam for diagram) Ted is traveling on his railroad car with speed 0.85c relative to Alice. Ted's trip lasts for 39 s as measured on his watch. Who measures the proper time of Ted's trip, Ted or Alice? How much time elapses on Alice's watch during this motion? A. Alice; 74 s B. Ted; 74 s C. Both; 29.7 s D. Ted; 29.7 s E. Alice; 29.7 s

B

(14C) A tank holds a layer of oil, of thickness T_0 = 1.66 m, that floats on a layer of syrup of thickness T_s = 0.700 m, as shown in the figure. Both liquids are clear and do not mix together. A light ray, originating at the bottom of the tank at point P, crosses the oil-syrup interface at a point 0.900 m from the axis. The ray continues and arrives at the oil-air interface, 2.00 m to the right of P and at the critical angle. What is the index of refraction of the oil? A. 1.85 B. 1.81 C. 1.77 D. 1.83 E. 1.79

B

(15C) A photon of blue light and a photon of red light are traveling in a vacuum. The photon of blue light A. has a longer wavelength than a photon of red light and travels with the same speed B. has smaller wavelength than a photon of red light and travels with the same speed C. has a smaller wavelength than a photon of red light and travels with a greater speed D. has a longer wavelength than a photon of red light and travels with a greater speed

B

(16A) What is the frequency of monochromatic light where the photon energy is 6.5 x 10^-19 J? A. 2.2 x 10^14 Hz B. 9.8 x 10^14 Hz C. 4.4 x 10^14 Hz D. 8.3 x 10^14 Hz E. need to know the work function

B

(16C) A blue laser beam is incident on a metallic surface, causing electrons to be ejected from the metal. If the frequency of the laser beam is increased wile the intensity of the beam is held fixed, A. the rate of ejected electrons will remain the same but their max kinetic energy will increase B. the rate of ejected electrons will decrease and their max kinetic energy will increase C. the rate of ejected electrons will remain the same, but their max kinetic energy will decrease D. the rate of ejected electrons will increase and their max kinetic energy will increase

B

(17A) Who was the first to successfully explain the photoelectric effect? A. Young B. Einstein C. Planck D. Bohr E. Hertz

B

(19A) The restriction that no more than one electron may occupy a given quantum state in an atom was first stated by which of the following scientists? A. Bohr B. Pauli C. de Broglie D. Heisenberg E. Planck

B

(22A) The binding energy of a nucleus is equal to: A. the mass of the nucleus times c^2 B. the energy needed to separate all the nucleons from each other C. the average energy with which any nucleon is bound in the nucleus D. the energy needed to remove one of the nucleons E. the mass of the protons times c^2

B

(27A) When an electric current exists within a conducting wire, which of the following statements describes the condition of any accompanying electric field? A. must be perpendicular to current flow B. must be parallel to current flow C. must be zero D. must be anti-parallel (opposite direction) to current flow E. must be cylindrical

B

(34A) A liquid has an index of refraction of 1.33. What is the speed of light through it? A. 3.99 x 10^8 m/s B. 2.26 x 10^8 m/s C. 4.46 x 10^8 m/s D. 2.04 x 10^8 m/s E. 3.00 x 10^8 m/s

B

(36A) A mass is bouncing on the end of a spring with a period T when measured by a ground observer. What would the period of oscillation be (as measured by the same observer) if the mass and spring were moving past the ground observer at a speed of 0.600c? A. 0.440 T B. 1.25 T C. 0.600 T D. 1.67 T E. 0.8 T

B

(4B Reference the exam for diagram) Two charges Q and nQ, where n = 3, are located as shown in the figure below. When a third charge is placed at the origin, it is found that force on it is zero. Find alpha A. 2.44 B. 1.73 C. 3 D. 3.46 E. 0.86

B

(5A) The path of a charged particle moving perpendicular to a uniform magnetic field will be a : A. ellipse B. circle C. straight line D. parabola E. hyperbola

B

(5C) A rod is 4.0m long and has a square cross section that is 1.5cm on each side. An ohmmeter measured 0.040 ohms across its ends. What is the resistivity of the material from which the rod is made? A. 0.023 ohm*m B. 2.3 x 10^-6 ohm*m C. 0.015 ohm*m D. 1.5 x 10^-4 ohm*m

B

(6C) A spaceship traveling at constant velocity passes by Earth and later passes by Mars. In which frame of reference is the amount of time separating these two events the proper time? A. any frame of reference, inertial or not B. the spaceship frame of reference C. any inertial frame of reference D. the Earth frame of reference E. the Mars frame of reference

B

(7C) A 14mm tall postage stamp is 4.0mm from a converging lens. If the image of the stamp is 4.0mm tall, how far is it from the lens? A. 1.4 mm B. 1.1 mm C. 14 mm D. 8.7 mm

B

(8A) The electric field E in an electromagnetic wave is oriented in what direction with respect to its associated magnetic field, B? A. E anti-parallel to B B. E perpendicular to B C. E at a 45 degree angle to B D. E parallel to B E. same direction

B

(8C) A small styrofoam ball of mass 0.12 g is placed in an electric field of 6000 N/C pointing downward. What excess charge must be placed on the ball for it to remain suspended in the field? A. -18.0 nC B. -196 nC C. -125 nC D. -16 nC E. -57.2 nC

B

(10C) Two equally charged tiny spheres of mass 1.0 g are placed 2.0 cm apart. When released, they begin to accelerate away from each other at 778 m/s^2. What is the magnitude of the charge on each sphere, assuming only that the electric force is present? (k = (1/4) * pi * e_0 = 9.0 x 10^9 (N*m^2)/C^2 A. 130 nC B. 160 nC C. 190 nC D. 100 nC

C

(11A) Which of the following colors is scattered most readily by small particles in the air? A. red B. yellow C. blue D. green E. scattering does not depend on color

C

(12C) A charged particle of mass 0.0050 kg is subjected to a 3.0 T magnetic field which acts at a right angle to its motion. If the particle moves in a circle of radius 0.10 m at a speed of 2.0 m/s, what is the magnitude of the charge on the particle? A. 2000 C B. 0.00050 C C. 0.033 C D. 30 C

C

(15A) Which of the following is an indication that one is dealing with a wave property instead of a particle property? A. energy B. quanta C. interference D. momentum E. photoelectric effect

C

(1B Reference the exam for drawing) A square loop of edge length L = 0.29 m with I = 3.9 A is pulled from a region where the magnetic field is zero into a region where the magnetic field is perpendicular to the loop with a magnitude of B = 2.5 T. What is the direction of the magnetic force on the loop? A. upwards B. downwards C. towards left D. towards right E. into the page

C

(20A) The atomic number, Z, of a given element is equivalent to which of the following? A. neutron number in the nucleus B. sum of the protons and neutrons in the nucleus C. proton number in the nucleus D. number of electrons in the outer shells E. number of electrons and protons

C

(23A) Two beams of coherent light are shining on the same piece of white paper. With respect to the crests and troughs of such waves, darkness will occur on the paper where: A. the crest from one wave overlaps with the crest from the other B. the troughs from both waves overlap C. the crest from one wave overlaps with the trough from the other D. darkness cannot occur as the two waves are coherent E. the sum of the positive and negative photons is zero

C

(24A) That all points on a wave front act as new sources of spherical waves is attributed to: A. Maxwell B. Young C. Huygens D. Rayleigh E. Michelson

C

(26A) If the distance between two point charges is quadrupled, the mutual force between them will be changed by what factor? A. 8 B. 4 C. 1/16 D. 1/4 E. 1/2

C

(2C) About 1350 W/m^2 of electromagnetic energy reaches the upper atmosphere of the Earth from the Sun, which is 1.5 x 10^11 m away. Use this info to estimate the average power output of the sun. A. 3 x 10^26 W B. 1 x 10^26 W C. 4 x 10^26 W D. 2 x 10^26 W

C

(30A) A proton moving at a speed of 3.8 x 10^6 m/s cuts across the lines of a magnetic field at an angle of 40 degrees. The strength of the field is 0.25 x 10^-4 T. What is the magnitude of the force acting on the proton? A. 1.4 x 10^-17 N B. 2.3 x 10^-17 N C. 9.8 x 10^-18 N D. 5.1 x 10^-18 N E. 1.52 x 10^-17 N

C

(31A) A uniform 4.5 T magnetic field passes through the plane of a wire loop 0.20 m^2 in area. What flux passes through the loop when the direction of the 4.5 T field is at a 30 degree angle to the normal of the loop plane? A. 0.39 T-m^2 B. 5.0 T-m^2 C. 0.78 T-m^2 D. 0.225 T-m^2 E. 0.9 T-m^2

C

(33A) An electromagnetic wave with a peak magnetic field component of 7.3 x 10^-7 T has an associated peak electric field component of what value? A. 45 N/C B. 2.0 x 10^-5 N/C C. 2.2 x 10^2 N/C D. 0.50 x 10^-15 N/C E. 1.4 x 10^-6 N/C

C

(3A) Three resistors connected in parallel each carry currents labeled I1, I2, and I3. Which of the following expresses the value of the total current IT in the combined system? A. IT = (1/I1 + 1/I2 + 1/I3) B. IT = I1 = I2 = I3 C. IT = I1 + I2 + I3 D. IT = (1/I1 + 1/I2 + 1/I3)^-1 E. need to know the voltage

C

(3C) A giant star radiates energy at the rate of 3.0 x 10^30 W, and its surface temperature has been measured to be 3000 K. Assuming that it is a perfect emitter, what is the radius of this star? (sigma = 5.67 x 10^-8 W/(m^2 * K^4) A. 1.4 x 10^10 m B. 1.9 x 10^11 m C. 2.3 x 10^11 m D. 7.8 x 10^10 m E. 8.7 x 10^10 m

C

(4A) If an electron is released at the equator and falls toward the Earth under the influence of gravity, the magnetic force on the electron will be toward the : A. south B. east C. west D. north E. ground

C

(9B) Find the wavelength of the radiation emitted when a hydrogen atom makes a transition from the n=5 to the n=3 state. A. 1.28 nm B. 1.81 nm C. 1.28 um D. 2.56 um E. 2.56 nm

C

(R10-5) Unpolarized light of intensity I_0 passes through two sheets of ideal polarizer. The angle between the polarizers axis is 30 degrees. What is the intensity of light after the second polarizer? A. 0 B. 0.25 I_0 C. 0.375 I_0 D. 0.5 I_0 E. 0.75 I_0

C

(R11-3) Electromagnetic waves contain: A. oscillating electric field B. oscillating magnetic field C. both A and B D. neither of the above

C

(R13-5) Which of the following statements about photons is true? A. we know some photons are waves because of Young's double slit interference experiment B. we know some photons are particles because of the photoelectric effect C. all photons have both wave-like and particle-like properties D. none of the above

C

(R14-7) The de Broglie wavelength of a 0.060 kg golf ball is 3.56 x 10^-34 m. What is its speed? (h = 6.63 x 10^-34 Js) A. 0.21 m/s B. 15.5 m/s C. 32 m/s D. 356 m/s

C

(R15-2) Which of the following is NOT a carbon isotope? A. ^12_6 C B. ^13_6 C C. ^13_7 C D. They're all isotopes of Carbon

C

(R9-2) Convex MIRROS produce: A. real images that are inverted B. real images that are upright C. virtual images that are upright D. virtual images that are inverted E. both A and C

C

(R9-5) concave LENS produce: A. real images that are inverted B. real images that are upright C. virtual images that are upright D. virtual images that are inverted E. both A and C

C

(11B) (a) Light of wavelength 480 nm is incident upon a metal that has a work function of 1.4 eV. What is the maximum speed of the emitted electrons? (enter zero if no electron are emitted.) (b) How would your answers to part (a) vary if the light intensity were doubled? A. 6.45 x 10^5 m/s; answer to part (a) is doubled B. 9.12 x 10^5 m/s; answer to part (a) is doubled C. 12.9 x 10^5 m/s; answer to part (a) is halved D. 6.45 x 10^5 m/s; no effect E. 9.12 x 10^5 m/s; no effect

D

(14A) The gravitational field is equivalent to: A. the inertial mass B. an event horizon C. a clock running slowly D. an accelerated frame of reference E. the proper time

D

(21A) The experiment, which gave the first evidence for the existence of the atomic nucleus, involved which of the following? A. X-ray scattering B. cosmic ray detection C. radioactive dating D. alpha scattering E. photoelectric effect

D

(2B Reference the exam for drawing) Three point charges are located near a spherical Gaussian surface of radius R = 6 cm. One charge (+3Q) is inside a sphere, and the others are a distance R/3 outside the surface. What is the electric flux through this surface (Q = 6 uC) ? A. 0.67 x 10^6 Nm^2/C B. 2.71 x 10^6 Nm^2/C C. 0 D. 2.03 x 10^6 Nm^2/C E. 3.39 x 10^6 Nm^2/C

D

(37A) If the measured momentum of an electron is 3.20 x 10^-27 kg*m/s with an uncertainty of 4.8 x 10^-28 kg*m/s, what is the minimum uncertainty in the position? A. 0.63 x 10^-4 m B. 2.2 x 10^-7 m C. 3.3 x 10^-6 m D. 1.1 x 10^-7 m E. 1.6 x 10^-8 m

D

(38A) The Lyman series of hydrogen corresponds to electron transitions from higher levels to n=1. What is the longest wavelength in that series? A. 91.4 nm B. 273 nm C. 456 nm D. 122 nm E. 73 nm

D

(7A) Consider an AC series circuit containing a coil, capacitor, and a resistor. Doubling the frequency will change the capacitance reactance by what factor? A. 1.41 B. 1.0 C. 2.0 D. 1/2 E. has no effect

D

(9C) A long vertical wire carries a steady 70 A current. As shown in the figure, a pair of horizontal rails of 0.20 m apart. A 20 ohm resistor connects points A and B, at the end of the rails. A bar is in contact with the rails, and is moved by an external force with a constant horizontal velocity of 0.90 m/s to the right, as shown. The bar and the rails have negligible resistance. At the instant that the bar is 0.20 m from the wire, what are the induced current in the resistor and its direction through the resistor? (mu_0 = 4*pi x 10^-7 T*m/A) A. 0.32 uA, from B to A B. 0.32 uA, from A to B C. 1.9 uA from B to A D. 0.63 uA, from A to B E. 0.63 uA, from B to A

D

(R10-4) In a Young's double slit experiment, both the wavelength and the slit separation are increased by 25%. What happens to the distance between two adjacent bright fringes? A. decreases by 50% B. increases by 50% C. distances increases by 25% or more D. distance stays the same

D

(R11-2) In a diffraction grating pattern, what wavelength of light produces largest separation between m = 0 and m = 1 bright bands? A. 400 nm (violet) B. 450 nm (blue) C. 550 nm (green) D. 650 nm (red)

D

(R15-3) Balance the following nuclear fission reaction: ^1_0 n + ^235_92 U ---- ^133_51 Sr + ^99_41 Nb + ???? A. 2 (^1_0 n) B. ^4_2 He C. y D. 4 (^1_0 n) E. e^-

D

(12B) Two spaceships are moving directly toward each other with a relative velocity of 0.8c. If an astronaut measures the length of his own spaceship to be 29 m, how long is the spaceship as measured by an astronaut in the other ship? A. 22.6 m B. 48.3 m C. 13.3 m D. 29 m E. 17.4 m

E

(13B) The intensity of moonlight when it reaches the Earth's surface is approximately 0.016 W/m^2 (for a full moon). What is the amplitude of the associated electric field? What is the amplitude of the associated magnetic field? A. E0 = 4.91 V/m; B0 = 2.3 x 10^-8 T B. E0 = 6.94 V/m; B0 = 1.15 x 10^-8 T C. E0 = 4.91 V/m; B0 = 1.63 x 10^-8 T D. E0 = 3.47 V/m; B0 = 1.63 x 10^-8 T E. E0 = 3.47 V/m; B0 = 1.15 x 10^-8 T

E

(17C) In a two slit experiment, the slit separation is 3.8 x 10^-5 m. The interference pattern is created on a screen that is 2.00 m away from the slits. If the 7th bright fringe on the screen is 10.0 cm away from the central fringe, what is the wavelength of the light? A. 261 nm B. 100 nm C. 281 nm D. 291 nm E. 271 nm

E

(25A) When a hydrogen atom absorbs a photon that raises it to the n=4 state, what is the least number of photons that can be emitted by that atom as it returns to the ground state? A. 4 B. 3 C. 5 D. 2 E. the correct value is not given

E

(3B Reference the exam for diagram) Consider the two wires in the figure. FOr what value of the ratio I1/I2, is the magnetic field zero at the point A? For what value of the ratio I1/I2, is the magnetic field zero at the point C? A. 0.33, 1 B. 1, -0.33 C. 0.33, -0.33 D. -0.33, 1 E. -0.33, 0.33

E

(4C) A spaceship is moving away from an asteroid with a speed of 0.8c relative to the asteroid. The spaceship then fires a missile with a speed of 0.5c relative to the spaceship. What is the speed of the missile measured by astronauts on the asteroid if the missile is fired away from the asteroid? A. 0.30c B. 0.65c C. 0.50c D. 1.3c E. 0.93c

E

(5B) Nuclei have energy levels just as atoms do. An excited nucleus can make a transition to a lower energy level by emitting a gamma-ray photon. The lifetime of a typical nuclear excited state is about 1 ps. What is the uncertainty in the energy of the gamma-rays emitted by a typical nuclear excited state? A. 4 x 10^-6 eV B. 8 x 10^-4 eV C. 1 x 10^-5 eV D. 5 x 10^-4 eV E. 3 x 10^-4 eV

E

(R11-5) If we decrease the amplitude of the electric field of an EM wave by a factor of 2 (by passing it through a polarizer) by what factor do we change the energy density of that wave? A. 4 (increases) B. 2 (increases) C. 1 (does not change energy density) D. 1/2 (decreases) E. 1/4 (decreases)

E

(R9-3) Concave MIRRORS produce: A. real images that are inverted B. real images that are upright C. virtual images that are upright D. virtual images that are inverted E. both A and C

E

(R9-4) convex LENS produce: A. real images that are inverted B. real images that are upright C. virtual images that are upright D. virtual images that are inverted E. both A and C

E

(R13-1) A 413.3 nm laser pulse is 100 nS long and carries 100 kW of power. Part a) what is teh energy of each pulse? Part b) how many photons are in each pulse?

E = 10 mJ, N = 2.1 x 10^16

(R11-4) The intensity of light is 0.017 W/m^2. What is the amplitude of its associated electric and magnetic field?

E = 3.58 V/m, B = 1.19 x 10^-8 T

(R15-7) In the figure below, a metal bar moves with velocity 5 m/s, while it is in contact with the two rods separated by 24 cm distance. What is the magnitude and direction of the current in the resistor, R = 12 ohm? Here, the magnetic field is constant, B = 1.2 T

I = 0.12 A, direction A to C

(R12-7) A barn is 20 m long and a pole is 25 m long with a diameter of 2 m at rest. I fthe pole is travelling at 0.7c towards the barn, what is the length and diameter of the pole as seen by a person standing outside the barn?

L = 18 m, D = 2 m

(R13-6) Estimate the power emitted by a human skin of area 1.0 cm^2. What wavelength of light is emitted at maximum intensity? (T_human_body = 37 celsius)

P = 5.25 x 10^-2 W, wavelength = 9.4 um

(R11-1) What is the higher order (m value) maximum for wavelength 450 nm that can be obtained with a grating with 300 lines per mm?

m = 7