Deck 17: Electromagnetic Waves

Question 1

Consider: radio waves (r), visible light (v), infrared (i), x-rays (x), and ultraviolet (u). In order of increasing frequency, they are:

A) r, v, i, x, u
B) r, i, v, u, x
C) i, r, v, u, x
D) i, v, r, u, x
E) r, i, v, x, u

Answer 1

r, i, v, u, x

Question 2

The order of increasing wavelength for blue (b), green (g), red (r), and yellow (y) light is:

A) r, y, g, b
B) r, g, y, b
C) g, y, b, r
D) b, g, y, r
E) b, y, g, r

Answer 2

b, g, y, r

Question 3

Of the following human eyes are most sensitive to:

A) red light
B) violet light
C) blue light
D) green light
E) none of these (they are equally sensitive to all colors)

Answer 3

green light

Question 4

Maxwell's equations predict that the speed of electromagnetic waves in free space is given by:

A)
B)
C)
D)
E)

Question 5

Radio waves differ from visible light waves in that radio waves:

A) travel slower
B) have a higher frequency
C) travel faster
D) have a lower frequency
E) require a material medium

Question 6

Radio waves of wavelength 3 cm have a frequency of:

A) 1 MHz
B) 9 MHz
C) 100 MHz
D) 10,000 MHz
E) 900 MHz

Question 7

An electromagnetic wave is generated by:

A) any moving charge
B) any accelerating charge
C) only a charge with changing acceleration
D) only a charge moving in a circle
E) only a charge moving in a straight line

Question 8

The electric field for a plane electromagnetic wave traveling in the +y direction is shown. Consider a point where is in the +z direction. The field is:

A) in the +x direction and in phase with the field
B) in the -x direction and in phase with the field
C) in the +x direction and 1/4 wave out of phase with the field
D) in the +z direction and in phase with the field
E) in the +z direction and 1/4 wave out of phase with the field

Question 9

A point source emits electromagnetic energy at a rate of 100 W. The intensity 10 m from the source is:

A) 10 W/m²
B) 1.6 W/m²
C) 1 W/m²
D) 0.024W/m²
E) 0.080 W/m²

Question 10

The light intensity 10 m from a point source is 1000 W/m². The intensity 100 m from the same source is:

A) 1000 W/m²
B) 100 W/m²
C) 10 W/m²
D) 1 W/m²
E) 0.1 W/m²

Question 11

When the distance between a point source of light and a light meter is reduced from 6.0 m to 2.0 m, the intensity of illumination at the meter will be the original value multiplied by:

A) 3
B) 9
C) 1/3
D) 1/9
E) 1

Question 12

Polarization experiments provide evidence that light is:

A) a longitudinal wave
B) a stream of particles
C) a transverse wave
D) some type of wave
E) nearly monochromatic

Question 13

A vertical automobile radio antenna is sensitive to electric fields that are polarized:

A) horizontally
B) in circles around the antenna
C) vertically
D) normal to the antenna in the forward direction
E) none of the above

Question 14

Light from any ordinary source (such as a flame) is usually:

A) unpolarized
B) plane polarized
C) circularly polarized
D) elliptically polarized
E) monochromatic

Question 15

The index of refraction of a substance is:

A) the speed of light in the substance
B) the angle of refraction
C) the angle of incidence
D) the speed of light in vacuum divided by the speed of light in the substance
E) measured in radians

Question 16

The units of index of refraction are:

A) m/s
B) s/m
C) radian
D) m/s²
E) none of these

Question 17

The diagram shows the passage of a ray of light from air into a substance X. The index of refraction of X is:

A) 0.53
B) 0.88
C) 1.9
D) 2.2
E) 3.0

Question 18

The index of refraction for diamond is 2.5. Which of the following is correct for the situation shown?

A) (sin a)/(sin b) = 2.5
B) (sin b)/(sin d) = 2.5
C) (cos a)/(cos c) = 2.5
D) (sin a)/(sin c) = 1/(2.5)
E) a/c = 2.5

Question 19

When light passes from air to glass, it bends:

A) toward the normal without changing speed
B) toward the normal and slows down
C) toward the normal and speeds up
D) away from the normal and slows down
E) away from the normal and speeds up

Question 20

The index of refraction of a certain glass is 1.50. The sine of the critical angle for total internal reflection at a glass-air interface is:

A) 0.50
B) 0.67
C) 0.75
D) 1.00
E) 1.50