physics : class12 Long-Wave Radio : Radio Waves : Electromagnetic Waves MCQ Questions and Answers
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Long-Wave Radio
MCQ questions and answers.
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MCQ Questions
1. Which type of radio wave has the longest wavelength among the following?
A.
Long-wave radio
B.
Medium-wave radio
C.
Short-wave radio
D.
Microwave
Correct Answer:
Long-wave radio
Explanation:
Long-wave radio is characterized by its very large wavelength compared with medium-wave, short-wave, and microwave radiation.
2. Long-wave radio signals generally have which frequency range?
A.
Very low frequency
B.
Very high frequency
C.
Only infrared frequency
D.
Only ultraviolet frequency
Correct Answer:
Very low frequency
Explanation:
Long wavelength and frequency are inversely related, so long-wave radio signals have relatively low frequencies.
3. How do long-wave radio signals mainly travel over the Earth's surface?
A.
As ground waves
B.
Only as straight-line rays
C.
Only through optical fibres
D.
As sound waves in air
Correct Answer:
As ground waves
Explanation:
Long-wave radio signals can follow the curvature of the Earth as ground waves, allowing them to travel beyond the horizon.
4. Why can long-wave radio signals travel around small obstacles more effectively than short-wave signals?
A.
They have longer wavelengths and undergo stronger diffraction
B.
They have no electric field
C.
They travel slower than sound
D.
They are not electromagnetic waves
Correct Answer:
They have longer wavelengths and undergo stronger diffraction
Explanation:
Long-wave radio signals bend around obstacles because their long wavelengths produce significant diffraction.
5. Which of the following is a common use of long-wave radio?
A.
Long-distance navigation signals
B.
Medical X-ray imaging
C.
Visible-light photography
D.
Ultraviolet sterilization
Correct Answer:
Long-distance navigation signals
Explanation:
Long-wave radio is useful for navigation and time-signal transmissions because the waves can travel long distances along the ground.
6. Compared with short-wave radio, long-wave radio usually requires which type of antenna for efficient transmission?
A.
A physically longer antenna
B.
A microscopic antenna
C.
No antenna
D.
Only a glass lens
Correct Answer:
A physically longer antenna
Explanation:
Efficient radio antennas are related to the wavelength of the signal, so the long wavelength of long-wave radio generally requires a larger antenna.
7. What happens to the frequency of a radio wave when its wavelength is increased, assuming its speed remains constant?
A.
The frequency decreases
B.
The frequency increases
C.
The frequency becomes zero
D.
The frequency becomes independent of wavelength
Correct Answer:
The frequency decreases
Explanation:
For electromagnetic waves, frequency and wavelength are inversely related by the relation v = fλ. Thus, a longer wavelength means a lower frequency when speed is constant.
8. Which property makes long-wave radio suitable for communication over curved terrain?
A.
Its ability to follow the Earth's surface
B.
Its ability to become visible to the eye
C.
Its production of heat only
D.
Its inability to diffract
Correct Answer:
Its ability to follow the Earth's surface
Explanation:
Long-wave radio signals propagate as ground waves and can follow the Earth's curved surface, making them suitable for communication over curved terrain.
9. Long-wave radio belongs to which part of the electromagnetic spectrum?
A.
The radio-wave region
B.
The gamma-ray region
C.
The X-ray region
D.
The visible-light region
Correct Answer:
The radio-wave region
Explanation:
Long-wave radio is a low-frequency, long-wavelength part of the electromagnetic spectrum.
10. Which statement about long-wave radio is correct?
A.
It can provide coverage beyond the line of sight through ground-wave propagation
B.
It can travel only in a vacuum
C.
It always has a shorter wavelength than microwaves
D.
It is a mechanical wave requiring air to propagate
Correct Answer:
It can provide coverage beyond the line of sight through ground-wave propagation
Explanation:
Long-wave radio is electromagnetic and can propagate as a ground wave, allowing it to reach regions beyond the direct line of sight.
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