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The MCQs below are drawn from the Physics subject category.
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1021
Two tuning forks have same natural frequency. One of them is now loaded with wax. When both the forks are sounded together, they will
A. remain in resonance
B. produce vibrations
C. produce interference
D. produce beats
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Correct Option
Explanation
Loading one fork changes its frequency slightly, so sounding both produces beats due to the frequency difference.
1022
The ratio of the velocity of sound in hydrogen to the velocity of sound in oxygen is
A. 2:1
B. 16:1
C. 4:1
D. 8:1
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Correct Option
Explanation
Speed of sound ∝ 1/√(molar mass); ratio v_H2/v_O2 = √(M_O2/M_H2) = √(32/2) = √16 = 4, so 4:1.
1023
Speed of sound in a gas is:
A. Directly proportional to absolute temperature (T)
B. Directly proportional to square root of T
C. Directly proportional to square of T
D. Inversely proportional to T
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Correct Option
Explanation
The speed of sound in a gas varies with the square root of absolute temperature, so option C is correct.
1024
The ratio of intensities of two sound waves is 4 : 9. What will be the ratio of their amplitudes?
A. 3:2
B. 2:3
C. 9:4
D. 4:9
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Correct Option
Explanation
Intensity ∝ amplitude^2, so amplitude ratio = sqrt(4:9) = 2:3.
1025
A table makes 5 rev/sec. A fork of frequency 1000 Hz is at a distance of 0.7 m from the axis of rotation on the table. The velocity of sound is 352 m/s. A man is standing at a little distance from the table. The maximum frequency noted by the man is
A. 1000 Hz
B. 941 Hz
C. 1033 Hz
D. 1067 Hz
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Correct Option
Explanation
Tangential speed = 2π·5·0.7 ≈ 21.99 m/s; f_max = f·(c/(c - v)) ≈ 1000·(352/(352-21.99)) ≈ 1067 Hz.
1026
Supposing a sitar string is plucked at about 1/4th of its length from the end. The most prominent harmonic would be
A. second
B. third
C. eighth
D. fourth
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Correct Option
Explanation
Plucking at L/4 gives harmonic amplitudes proportional to sin(nπ/4)/n^2; among the listed overtones the second harmonic has the largest amplitude, so the second is most prominent.
1027
In a resonance column, first and second resonances are obtained at depths 22.7 cm and 70.2 cm respectively. The third resonance will be obtained at a depth
A. 92.9 cm
B. 117.7 cm
C. 113.5 cm
D. 115.5 cm
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Correct Option
Explanation
The spacing between successive resonance depths is λ/2 = 70.2 − 22.7 = 47.5 cm, so the third resonance is at 70.2 + 47.5 = 117.7 cm.
1028
In a Kundt's tube, the length of the iron rod is 1 m. The stationary waves of frequency 2500 Hz are produced in it. The velocity of sound in iron is
A. 5000 m s^-1
B. 2500 m s^-1
C. 1250 m s^-1
D. 10000 m s^-1
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Correct Option
Explanation
For a rod of length L with standing longitudinal wave fundamental wavelength λ = 2L, so v = fλ = 2500 × 2 × 1 = 5000 m/s.
1029
The ratio of the fundamental frequency of an open end and closed end organ pipes of the same length is:
A. 1:1
B. 4:1
C. 2:1
D. 1:2
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Correct Option
Explanation
For the same length, f_open = v/(2L) and f_closed = v/(4L), so the open:closed fundamental ratio is 2:1; OCR marks this option.
1030
Decibel is the unit of
A. Sound
B. Heat
C. Electricity
D. None of these
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Correct Option
Explanation
The decibel is a logarithmic unit used to measure sound intensity.
