1. What form of energy is carried by a radio wave?
A.
Electromagnetic energy
B.
Chemical energy
C.
Nuclear energy
D.
Mechanical energy only
Correct Answer:
Electromagnetic energy
Explanation:
A radio wave is an electromagnetic wave, so it carries electromagnetic energy through space.
2. The energy carried by a radio wave is transported by its:
A.
Electric and magnetic fields
B.
Material particles
C.
Sound vibrations
D.
Gravitational field only
Correct Answer:
Electric and magnetic fields
Explanation:
Radio-wave energy is transported through the oscillating electric and magnetic fields of the electromagnetic wave.
3. If the amplitude of the electric field of a radio wave increases, its intensity generally:
A.
Increases
B.
Decreases to zero
C.
Remains unchanged
D.
Becomes negative
Correct Answer:
Increases
Explanation:
The intensity, or energy flow per unit area, of an electromagnetic wave increases with the square of its field amplitude.
4. The intensity of a radio wave is defined as the energy transmitted per unit:
A.
Area per unit time
B.
Mass per unit volume
C.
Charge per unit length
D.
Frequency per unit wavelength
Correct Answer:
Area per unit time
Explanation:
Wave intensity measures the rate at which energy passes through a unit area.
5. For a radio source radiating uniformly in all directions, the intensity decreases with distance because the energy spreads over a larger:
A.
Surface area
B.
Frequency
C.
Wavelength
D.
Electric charge
Correct Answer:
Surface area
Explanation:
As the distance from an isotropic radio source increases, the same emitted energy spreads over a larger spherical surface area.
6. At twice the distance from an isotropic radio transmitter, the radio-wave intensity becomes:
A.
One-fourth as large
B.
Twice as large
C.
Four times as large
D.
Unchanged
Correct Answer:
One-fourth as large
Explanation:
For uniform radiation, intensity follows the inverse-square law, so doubling the distance reduces intensity to one-fourth.
7. Which radio wave carries more energy per photon?
A.
The radio wave with higher frequency
B.
The radio wave with lower frequency
C.
Both always carry equal photon energy
D.
The radio wave with greater amplitude only
Correct Answer:
The radio wave with higher frequency
Explanation:
The energy of one photon is proportional to frequency according to E = hf.
8. Compared with visible-light photons, photons of ordinary radio waves generally have:
A.
Lower energy
B.
Higher energy
C.
The same energy
D.
No electromagnetic energy
Correct Answer:
Lower energy
Explanation:
Radio waves have much lower frequencies than visible light, so each radio photon has less energy.
9. If the power emitted by a radio transmitter increases while the distance remains fixed, the radio-wave intensity generally:
A.
Increases
B.
Decreases
C.
Becomes zero
D.
Remains fixed in every case
Correct Answer:
Increases
Explanation:
At a fixed distance, a transmitter emitting more power sends more energy per unit time, increasing the intensity.
10. Which quantity indicates how much radio-wave energy passes through a unit area in one second?
A.
Intensity
B.
Wavelength
C.
Frequency
D.
Period
Correct Answer:
Intensity
Explanation:
Intensity is the energy transferred per unit area per unit time, so it describes the energy flow of a radio wave.
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