1. Short-wave radio signals generally have frequencies in which range?
A.
3 MHz to 30 MHz
B.
3 kHz to 30 kHz
C.
30 MHz to 300 MHz
D.
300 MHz to 3 GHz
Correct Answer:
3 MHz to 30 MHz
Explanation:
Short-wave radio commonly refers to radio waves with frequencies from about 3 MHz to 30 MHz.
2. What is the approximate wavelength range of short-wave radio signals in free space?
A.
1 mm to 1 cm
B.
10 m to 100 m
C.
1 km to 10 km
D.
1000 km to 10,000 km
Correct Answer:
10 m to 100 m
Explanation:
Using the relation c = fλ, frequencies from 3 MHz to 30 MHz correspond approximately to wavelengths from 100 m to 10 m.
3. Which atmospheric region is mainly responsible for the long-distance propagation of short-wave radio signals?
A.
Troposphere
B.
Stratosphere
C.
Ionosphere
D.
Mesosphere only
Correct Answer:
Ionosphere
Explanation:
The ionosphere can refract or return suitable short-wave radio signals toward Earth, allowing communication over long distances.
4. Short-wave radio is especially useful for communication over
A.
Only a few centimeters
B.
Only within a single room
C.
Very long distances
D.
Only underwater distances
Correct Answer:
Very long distances
Explanation:
Short-wave signals can travel beyond the horizon by interacting with the ionosphere, making them useful for long-distance communication.
5. Which type of propagation allows a short-wave signal to return to Earth from the ionosphere?
A.
Ground-wave propagation only
B.
Sky-wave propagation
C.
Sound-wave propagation
D.
Optical-fibre propagation
Correct Answer:
Sky-wave propagation
Explanation:
In sky-wave propagation, short-wave radio signals are refracted by the ionosphere and return to Earth at distant locations.
6. Why can short-wave radio communication cover distances beyond the visible horizon?
A.
The signals travel only through cables
B.
The signals are reflected or refracted by the ionosphere
C.
The signals stop at the horizon and disappear
D.
The signals are converted into sound in space
Correct Answer:
The signals are reflected or refracted by the ionosphere
Explanation:
Ionospheric interaction bends suitable short-wave signals back toward Earth, enabling communication beyond the line of sight.
7. Which of the following is a common application of short-wave radio?
A.
International broadcasting
B.
Illuminating rooms
C.
Measuring body temperature
D.
Producing X-ray images
Correct Answer:
International broadcasting
Explanation:
Short-wave radio is widely used for broadcasting over very large distances, including international broadcasts.
8. The ability of short-wave radio to travel long distances depends strongly on
A.
The condition of the ionosphere
B.
The color of the transmitter
C.
The temperature of a battery alone
D.
The size of a loudspeaker only
Correct Answer:
The condition of the ionosphere
Explanation:
The ionosphere's level of ionization affects how short-wave signals are refracted and how far they can propagate.
9. Which statement about short-wave radio signals is correct?
A.
They have much longer wavelengths than radio waves used for long-wave broadcasting
B.
They can use the ionosphere for long-distance communication
C.
They cannot travel beyond the transmitter's immediate surroundings
D.
They belong to the visible-light region
Correct Answer:
They can use the ionosphere for long-distance communication
Explanation:
A key feature of short-wave radio is its ability to use ionospheric propagation for communication over large distances.
10. What usually happens to a short-wave radio signal after it is refracted by the ionosphere?
A.
It may return to Earth's surface at a distant location
B.
It changes into a water wave
C.
It becomes a permanent electric current
D.
It is absorbed immediately by the loudspeaker
Correct Answer:
It may return to Earth's surface at a distant location
Explanation:
Ionospheric refraction can bend a short-wave signal back toward Earth, allowing it to be received far from the transmitter.
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