24.2 Production of Electromagnetic Waves
If an electromagnetic wave is described as having a frequency of 3 GHz, what are its period and wavelength (in a vacuum)?
- 3.0 × 109s, 10 cm
- 3.3 × 10−10s, 10 cm
- 3.3 × 10−10s, 10 m
- 3.0 × 109s, 10 m
Describe the outcome if you attempt to produce a longitudinal electromagnetic wave.
A wave is travelling through a medium until it hits the end of the medium and there is nothing but vacuum beyond. What happens to a mechanical wave? Electromagnetic wave?
- reflects backward, continues on
- reflects backward, reflects backward
- continues on, continues on
- stops, continues on
You’re on the moon, skipping around, and your radio breaks. What would be the best way to communicate this problem to your friend, who is also skipping around on the moon: yelling or flashing a light? Why?
Given the waveform in Figure 24.5(d), if GHz and , what is the correct equation for the magnetic field wave at the antenna?
The sun is far away from the Earth, and the intervening space is very close to empty. Yet the tilt of the Earth’s axis of rotation relative to the sun results in seasons. Explain why, given what you have learned in this section.
24.3 The Electromagnetic Spectrum
The correct ordering from least to greatest wavelength is:
- ELF, FM radio, microwaves, infrared, red, green, ultraviolet, x-ray, gamma ray
- ELF, FM radio, microwaves, infrared, green, red, ultraviolet, x-ray, gamma ray
- gamma ray, x-ray, ultraviolet, red, green, infrared, microwaves, FM radio, ELF
- gamma ray, x-ray, ultraviolet, green, red, infrared, microwaves, FM radio, ELF
Describe how our vision would be different if we could see energy in what we define as the radio spectrum.
24.4 Energy in Electromagnetic Waves
An old microwave oven outputs only half the electric field it used to. How much longer does it take to cook things in this microwave oven?
- Four times as long
- Twice as long
- Half the time
- One fourth the time
Describe at least two improvements you could make to a radar set to make it more sensitive (able to detect things at longer ranges). Explain why these would work.