MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question.

Transcription

1 Exam Name MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question. 1) A Hz electromagnetic wave propagates in carbon tetrachloride with a speed of m/s. The wavelength of the wave in carbon tetrachloride is closest to: A) 1070 nm B) 1290 nm C) 1200 nm D) 967 nm E) 1420 nm 1) 2) A Hz electromagnetic wave propagates in carbon tetrachloride with a speed of m/s. The wavelength of the wave in vacuum is closest to: A) 413 nm B) 368 nm C) 505 nm D) 459 nm E) 314 nm 2) 3) A Hz electromagnetic wave propagates in carbon tetrachloride with a speed of m/s. The relative magnetic permeability of carbon tetrachloride is The dielectric constant of carbon tetrachloride at a frequency of Hz is closest to: A) 2.52 B) 1.38 C) 1.76 D) 2.14 E) 1 4) A planar electromagnetic wave is propagating in the positive x-direction. At a certain point P and at a given instant, the electric field of the wave is given by E = -j 82 mv/m. The magnetic vector of the wave, at the point P at that instant is closest to: A) ( T) k B) ( T) k C) ( T) j D) ( T) j E) ( T) k 3) 4) 5) A planar electromagnetic wave is propagating in the positive x-direction. At a certain point P and at a given instant, the electric field of the wave is given by E = -j 12 mv/m. The Poynting vector at the point P at that instant is closest to: 5) A) ( W/m 2 ) i B) ( W/m 2 ) i C) ( W/m 2 ) k D) ( W/m 2 ) i E) ( W/m 2 ) i 1

2 6) The magnitude of the Poynting vector of a planar electromagnetic wave has an average value of 724 mw/m 2. The maximum value of the magnetic field in the wave is closest to: A) T B) T C) T D) T E) T 6) 7) The magnitude of the Poynting vector of a planar electromagnetic wave has an average value of 939 mw/m 2. The wave is incident upon a rectangular area, 1.5 m by 2.0 m, at right angles. The total energy that traverses the area in a time interval of one minute is closest to: A) 210 J B) 340 J C) 300 J D) 170 J E) 250 J 8) An 800-kHz radio signal is detected at a point 4.5 km distant from a transmitter tower. The electric field amplitude of the signal at that point is 630 mv/m. Assume that the signal power is radiated uniformly in all directions and that radio waves incident upon the ground are completely absorbed. The magnetic field amplitude of the signal at that point, in nt, is closest to: A) 2.5 B) 2.1 C) 1.7 D) 1.3 E) 2.9 7) 8) 9) An 800-kHz radio signal is detected at a point 8.5 km distant from a transmitter tower. The electric field amplitude of the signal at that point is 900 mv/m. Assume that the signal power is radiated uniformly in all directions and that radio waves incident upon the ground are completely absorbed. The average electromagnetic energy density at that point is closest to: A) J/m 3 B) J/m 3 C) J/m 3 D) J/m 3 E) J/m 3 9) 10) An 800-kHz radio signal is detected at a point 2.7 km distant from a transmitter tower. The electric field amplitude of the signal at that point is 360 mv/m. Assume that the signal power is radiated uniformly in all directions and that radio waves incident upon the ground are completely absorbed. The intensity of the radio signal at that point is closest to: A) W/m 2 B) W/m 2 C) W/m 2 D) W/m 2 E) W/m 2 10) 2

3 11) An 800-kHz radio signal is detected at a point 9.1 km distant from a transmitter tower. The electric field amplitude of the signal at that point is 440 mv/m. Assume that the signal power is radiated uniformly in all directions and that radio waves incident upon the ground are completely absorbed. The average total power radiated by the transmitter is closest to: A) W B) W C) W D) W E) W 11) Figure 32.1 A radiometer has two square vanes (1 cm by 1 cm), attached to a light horizontal cross arm, and pivoted about a vertical axis through the center. The center of each vane is 6 cm from the axis. One vane is silvered and it reflects all radiant energy incident upon it. The other vane is blackened and it absorbs all incident radiant energy. Radiant energy, which has an intensity of 300 W/m 2, is incident normally upon the vanes. 12) In Fig. 32.1, the radiant power absorbed by the blackened vane is closest to: A) 0.03 W B) 0.06 W C) 0.05 W D) 0.04 W E) 0.09 W 12) 13) In Fig. 32.1, the radiation pressure on the blackened vane is closest to: A) Pa B) Pa C) Pa D) Pa E) Pa 13) 14) In Fig. 32.1, the torque on the vane assembly, about the vertical axis, is closest to: A) zero B) N m C) N m D) N m E) N m 14) 3

4 15) The wavelength of visible light ranges from 400 nm to 700 nm. The highest frequency of visible light is closest to: A) Hz B) Hz C) Hz D) Hz E) Hz 15) 16) If the z-component of the magnetic field of an electromagnetic wave traveling in the x-direction through vacuum obeys the equation 16) B z = (1.25 µt) cos[(3800 m-1)x - ( rad/s)t], then the largest that the y-component of the electric field can be is closest to: A) 375 N/C B) N/C C) N/C D) N/C E) N/C Situation 32.1 A microwave oven operates at a frequency of 2400 MHz. The height of the oven cavity is 25 cm and the base measures 30 cm by 30 cm. Assume that microwave energy is generated uniformly on the upper surface of the cavity and propagates directly downward toward the base. The base is lined with a material that completely absorbs microwave energy. The total microwave energy content of the cavity is 0.50 mj. 17) In Situation 32.1, the power output of the microwave oven is closest to: A) 700 W B) 550 W C) 600 W D) 650 W E) 500 W 17) 18) In Situation 32.1, the intensity of the microwave beam is closest to: A) 5200 W/m 2 B) 7200 W/m 2 C) 6200 W/m 2 D) 6700 W/m 2 E) 5700 W/m 2 18) 19) In Situation 32.1, the electric field amplitude is closest to: A) 1600 V/m B) 2500 V/m C) 1900 V/m D) 2200 V/m E) 2800 V/m 19) 4

5 20) In Situation 32.1, the force on the base due to the radiation is closest to: A) N B) N C) N D) N E) N 20) 21) A Hz laser emits a 8.7-µs pulse, 5.0 mm in diameter, with a beam energy density of 0.21 J/m 3. The number of wavelengths in the length of the beam is closest to: A) B) C) D) E) ) 22) A Hz laser emits a 2.0-µs pulse, 5.0 mm in diameter, with a beam energy density of 0.75 J/m 3. The power emitted by the laser is closest to: A) 4.4 kw B) 13 kw C) 22 kw D) 8.9 kw E) 18 kw 22) 23) A Hz laser emits a 7.7-µs pulse, 5.0 mm in diameter, with a beam energy density of 0.51 J/m 3. The amplitude of the electric field of the emitted waves is closest to: A) V/m B) V/m C) V/m D) V/m E) V/m 23) 24) A 8.6 x Hz laser emits a 9.7 µs pulse, 5.0 mm in diameter, with a beam energy density of 0.85 J/m 3. The average Poynting vector magnitude of the beam is closest to: A) W/m 2 B) W/m 2 C) W/m 2 D) W/m 2 E) W/m 2 24) 5

6 Situation 32.2 A standing planar electromagnetic wave is established in a resonant cavity formed by two parallel conducting plates that are 12 cm apart. The number of electric field antinoidal planes, including the cavity walls, in the standing wave is three. 25) In Situation 32.2, the frequency of the electromagnetic wave in GHz (G = giga = 10 9 ), is closest to: A) 5.00 B) 3.75 C) 6.25 D) 2.50 E) ) 26) In Situation 32.2, the number of antinoidal planes for the magnetic field is: A) 4 B) 3 C) 5 D) 6 E) 2 26) 27) In Situation 32.2, the smallest distance between an electric field antinoidal plane and a magnetic field antinoidal plane, in cm, is closest to: A) zero B) 2.0 C) 1.0 D) 3.0 E) ) 28) A certain glass has an index of refraction of 1.44 at a wavelength of 560 nm in vacuum. What is the effective dielectric constant at the corresponding frequency? A) 2.07 B) 1.44 C) 3.66 D) 1.98 E) ) 29) Electromagnetic standing waves are set up in a conducting cavity resonator in the form of a hollow metal box. The waves bounce back and forth between two parallel surfaces separated by 0.80 cm. What is the minimum resonant frequency for such a resonator? A) 15.5 GHz B) 4.42 GHz C) 18.8 GHz D) 12.4 GHz E) 3.30 GHz 29) Situation 32.3 The y-component of the electric field of an electromagnetic wave traveling in the +x-direction through vacuum obeys the equation E y = (375 N/C) cos[ks - ( rad/s)t]. 30) In Situation 32.3, the wavelength of the electromagnetic wave is closest to: A) 2.72 µm B) 1.36 µm C) 8.57 µm D) 17.1 µm E) µm 30) 31) In Situation 32.3, the largest that the x-component of the magnetic field of the wave can be is closest to: A) 1.36 µt B) 1.25 µt C) T D) T E) 0.00 µt 32) In Situation 32.3, the largest that the z-component of the magnetic field of the wave can be is closest to: A) T B) 1.25 µt C) 0.00 µt D) 1.36 µt E) T 31) 32) 6

7 33) When an electromagnetic wave falls on a white, perfectly reflecting surface, it exerts a force F on that surface. If the surface is now painted a perfectly absorbing black, the force that the same wave would exert on the surface is: A) 4F B) F/2 C) F/4 D) 2F E) F 33) SHORT ANSWER. Write the word or phrase that best completes each statement or answers the question. 34) A sinusoidal electromagnetic wave is propagating in vacuum. (a) At a given point and at a particular time the electric field is in the +x-direction and the magnetic field is in the -y-direction. What is the direction of propagation of the wave? (b) At the above point the intensity of the wave is 0.86 W m-2. What is the electric field amplitude at this point? (Note: µo = 4π 10-7 T m/a and c = m/s) 34) 35) An electromagnetic wave has a wavelength of m in air and a wavelength of m in a certain dielectric material. Find the dielectric constant for the material. 35) 36) A source of light produces an electric field amplitude of 9.10 V/m 44.0 m from the source. What is the power output from the source? 36) 37) A totally absorbing surface of area A = 7.7 cm 2 faces a small source of sinusoidal electromagnetic radiation that is 2.4 m away. At the surface A the electric field amplitude of the radiation is 84 V/m. (Note: µ0 = 4π 10-7 T m/a and c = m/s.) (a) What is the radiation pressure exerted on the surface? (b) What is the total power output of the source, if it is assumed to radiate uniformly in all directions? 38) An electromagnetic standing wave is resonating in a cavity with n = 1. The nodal plane of the E field and the closest nodal plane of the B field are separated by 0.87 m. (a) Find the length of the resonating cavity. (b) Find the frequency of the electromagnetic wave. 37) 38) 39) A laser beam has a wavelength of 633 nm and a power of mw spread uniformly over a circle 1.20 mm in diameter. This beam falls perpendicularly on a perfectly reflecting piece of paper having twice the diameter of the laser beam and a mass of 1.50 mg. (a) What are the amplitudes of the electric and magnetic fields in this laser beam? (b) What acceleration does the laser beam give to the paper? 39) 7

8 Answer Key Testname: UNTITLED4 1) D 2) D 3) D 4) A 5) A 6) A 7) D 8) B 9) C 10) A 11) B 12) A 13) B 14) B 15) A 16) A 17) C 18) D 19) D 20) A 21) E 22) A 23) E 24) C 25) B 26) A 27) B 28) A 29) C 30) C 31) E 32) B 33) A 34) (a) -z-direction (b) 25 V/m 35) ) 2670 W 37) (a) Pa (b) watts 38) (a) 1.74 m (b) Hz 39) (a) E max = 577 N/C, B max = 1.92 µt (b) m/s 2 8