Chapter 32

In an electromagnetic wave, the electric and magnetic fields are oriented such that they are A) perpendicular to one another and parallel to the direction of wave propagation. B) perpendicular to one another and perpendicular to the direction of wave propagation. C) parallel to one another and parallel to the direction of wave propagation. D) parallel to one another and perpendicular to the direction of wave propagation.

perpendicular to one another and perpendicular to the direction of wave propagation.

An electromagnetic wave propagates along 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) +y B) +x C) -z D) +z E) -x

+x

If an electromagnetic wave has components Ey = E0 sin(kx - ωt) and Bz = B0 sin(kx - ωt) , in what direction is it traveling? A) +x B) -x C) -y D) +z E) +y

+x

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 What is the electric field amplitude at this point? (Note: and A) (a) -x-direction (b) 50 V/m B) (a) -z-direction (b) 25 V/m C) (b) +z-direction (b) 25 V/m D) (a) +y - direction; (b) 12.5 V/m

-z-direction (b) 25 V/m

If the magnetic field of an electromagnetic wave is in the +x-direction and the electric field of the wave is in the +y-direction, the wave is traveling in the A) -x-direction. B) +z-direction. C) -y-direction. D) -z-direction. E) xy-plane.

-z-direction.

An electromagnetic wave has a wavelength of 2.90 × 10-5 m in air and a wavelength of in a certain dielectric material. Find the dielectric constant for the material. A) 1.67 B) 1.74 C) 2.78 D) 0.60

2.78

A planar electromagnetic wave is propagating in the +x direction. At a certain point P and at a given instant, the electric field of the wave is given by = (0.082 V/m) . What is the magnetic vector of the wave at the point P at that instant? (c = 3.0 x 108 m/s) A) -0.27 nT B) 0.27 nT C) 0.27 nT D) -6.8 nT E) 6.8 nT

0.27 nT k

If a beam of electromagnetic radiation has an intensity of 120 W/m2, what is the maximum value of the electric field? (c = 3.0 x 108 m/s, μ0 = 4π × 10-7 T ∙ m/A, ε0 = 8.85 × 10-12 C2/N ∙ m2) A) 1.5 kV/m B) 0.0032 V/m C) 1.0 µV/m D) 1.0 µT E) 0.30 kV/m

0.30 kV/m

If the intensity of an electromagnetic wave is 80 MW/m2, what is the amplitude of the magnetic field of this wave? (c = 3.0 x 108 m/s, μ0 = 4π × 10-7 T ∙ m/A, ε0 = 8.85 × 10-12 C2/N ∙ m2) A) 0.82 mT B) 14 T C) 0.58 mT D) 10 T E) 0.33 µT

0.82 mT

The electric field amplitude near a certain radio transmeter is 3.85 × 10-3 V/m. What is the amplitude of the magnetic field? A) 1.92 × 10-12 B) 3.85 × 10-8 C) 1.28 × 10-11 D) 4.50 × 10-9

1.28 × 10-11

If the electric field and magnetic field of an electromagnetic wave are given by E = E0 sin(kx - ωt) and B = B0 sin(kx - ωt), and if the value of E0 is 51 µV/m, what is the value of B0? (c = 3.0 x 108 m/s) Question options: A) 1.7 × 103 T B) 1.7 × 10-13 T C) 1.7 × 1014 T D) 1.7 × 104 T E) 1.7 × 10-14 T

1.7 × 10-13 T

The magnitude of the electric field at a point P for a certain electromagnetic wave is 570 N/C. What is the magnitude of the magnetic field for that wave at P? (c = 3.0 x 108 m/s) A) 1.10 µT B) 2.41 µT C) 1.41 µT D) 1.90 µT E) 2.91 µT

1.90 µT

An electromagnetic wave has a peak electric field of 3.0 kV/m. What is the intensity of the wave? (c = 3.0 x 108 m/s, μ0 = 4π × 10-7 T ∙ m/A, ε0 = 8.85 × 10-12 C2/N ∙ m2) A) 8.0 kW/m2 B) 24 kW/m2 C) 12 kW/m2 D) 4.0 kW/m2

12 kW/m2

A source of light produces electric field amplitude of 9.10 V/m, 44 m from the source. What is the power output from the source? A) 0.2672 W B) 267.2 W C) 26.72 W D) 2672 W

2672 W

The magnetic field of an electromagnetic wave has a peak value of 5.0 × 10-10 T. What is the intensity of the wave? (c = 3.0 x 108 m/s, c = 3.00 × 108 m/s, μ0 = 4π × 10-7 T ∙ m/A, ε0 = 8.85 × 10-12 C2/N ∙ m2) A) 1.0 × 10-13 W/m2 B) 2.0 × 10-13 W/m2 C) 7.5 × 105 W/m2 D) 3.0 × 10-5 W/m2 E) 1.5 × 10-5 W/m2

3.0 × 10-5 W/m2

The magnitude of the magnetic field at point P for a certain electromagnetic wave is 2.12 μT. What is the magnitude of the electric field for that wave at P? (c = 3.0 x 108 m/s) A) 745 N/C B) 5.23 µN/C C) 7.45 µN/C D) 636 N/C E) 6.36 µN/C

636 N/C

Given that the wavelengths of visible light range from 400 nm to 700 nm, what is the highest frequency of visible light? (c = 3.0 x 108 m/s) A) 2.3 × 1020 Hz B) 5.0 × 108 Hz C) 7.5 × 1014 Hz D) 3.1 × 108 Hz E) 4.3 × 1014 Hz

7.5 × 1014 Hz

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, what will be the force that the same wave will exert on the surface? A) F/4 B) 2F C) F D) F/2 E) 4F

F/2

The energy per unit volume in an electromagnetic wave is A) all in the magnetic field. B) mostly in the magnetic field. C) mostly in the electric field. D) all in the electric field. E) equally divided between the electric and magnetic fields.

equally divided between the electric and magnetic fields.

An electromagnetic wave is propagating towards the west. At a certain moment the direction of the magnetic field vector associated with this wave points vertically up. The direction of the electric field vector of this wave is A) horizontal and pointing north. B) vertical and pointing up. C) horizontal and pointing south. D) vertical and pointing down. E) horizontal and pointing east.

horizontal and pointing south.

Which one of the following lists is a correct representation of electromagnetic waves from longer wavelength to shorter wavelength? A) radio waves, microwaves, infrared, visible, UV, X-rays, gamma rays B) radio waves, infrared, X-rays, microwaves, UV, visible, gamma rays C) radio waves, UV, X-rays, microwaves, infrared, visible, gamma rays D) radio waves, microwaves, visible, X-rays, infrared, UV, gamma rays E) radio waves, infrared, microwaves, UV, visible, X-rays, gamma rays

radio waves, microwaves, infrared, visible, UV, X-rays, gamma rays

A capacitor is hooked up to a resistor and an AC voltage source as shown in the figure. The output of the source is given by V(t) = V0 sin ωt. The plates of the capacitor are disks of radius R. Point P is directly between the two plates, equidistant from them and a distance R/2 from the center axis. At point P Question options: A) there is no magnetic field because there is no charge moving between the plates. B) there is a constant magnetic field. C) there is a time-varying magnetic field.

there is a time-varying magnetic field.