physics : class12 Radio Wave Wavelength : Radio Waves : Electromagnetic Waves MCQ Questions and Answers
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Radio Wave Wavelength
MCQ questions and answers.
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MCQ Questions
1. What is the relation between the wavelength, frequency, and speed of a radio wave?
A.
λ = cf
B.
λ = c/f
C.
λ = f/c
D.
λ = c + f
Correct Answer:
λ = c/f
Explanation:
The wavelength of a radio wave is given by λ = c/f, where c is the speed of the wave and f is its frequency.
2. A radio wave has a frequency of 100 MHz. What is its wavelength in vacuum? Take the speed of light as 3 × 10^8 m/s.
A.
0.3 m
B.
3 m
C.
30 m
D.
300 m
Correct Answer:
3 m
Explanation:
Using λ = c/f, λ = (3 × 10^8)/(100 × 10^6) = 3 m.
3. If the frequency of a radio wave is doubled, what happens to its wavelength in vacuum?
A.
It becomes twice as large
B.
It becomes half as large
C.
It remains unchanged
D.
It becomes four times as large
Correct Answer:
It becomes half as large
Explanation:
Since wavelength is inversely proportional to frequency when the wave speed is constant, doubling the frequency halves the wavelength.
4. A radio wave has a frequency of 150 MHz. What is its wavelength in vacuum?
A.
0.5 m
B.
2 m
C.
4.5 m
D.
45 m
Correct Answer:
2 m
Explanation:
Using λ = c/f, λ = (3 × 10^8)/(150 × 10^6) = 2 m.
5. Which radio wave has the longest wavelength?
A.
A wave of frequency 10 MHz
B.
A wave of frequency 50 MHz
C.
A wave of frequency 100 MHz
D.
A wave of frequency 200 MHz
Correct Answer:
A wave of frequency 10 MHz
Explanation:
For radio waves traveling at the same speed, lower frequency corresponds to longer wavelength.
6. What is the wavelength of a radio wave with a frequency of 300 MHz in vacuum?
A.
0.1 m
B.
1 m
C.
10 m
D.
100 m
Correct Answer:
1 m
Explanation:
Using λ = c/f, λ = (3 × 10^8)/(300 × 10^6) = 1 m.
7. A radio wave has a wavelength of 6 m in vacuum. What is its frequency?
A.
5 MHz
B.
18 MHz
C.
50 MHz
D.
180 MHz
Correct Answer:
50 MHz
Explanation:
Using f = c/λ, f = (3 × 10^8)/6 = 5 × 10^7 Hz = 50 MHz.
8. Which unit is commonly used to express the wavelength of a radio wave?
A.
Metre
B.
Hertz
C.
Watt
D.
Coulomb
Correct Answer:
Metre
Explanation:
Wavelength is a distance, so its SI unit is the metre (m).
9. A radio wave has a wavelength of 30 m. What is its frequency in vacuum?
A.
1 MHz
B.
10 MHz
C.
30 MHz
D.
90 MHz
Correct Answer:
10 MHz
Explanation:
Using f = c/λ, f = (3 × 10^8)/30 = 1 × 10^7 Hz = 10 MHz.
10. Two radio waves travel through vacuum. Wave X has a wavelength of 4 m, and wave Y has a wavelength of 8 m. Which wave has the higher frequency?
A.
Wave X
B.
Wave Y
C.
Both have the same frequency
D.
Their frequencies cannot be compared
Correct Answer:
Wave X
Explanation:
In vacuum, frequency is inversely proportional to wavelength. Therefore, the wave with the shorter wavelength, Wave X, has the higher frequency.
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