Verified past-paper data not yet uploaded
No verified paper has been uploaded for AJKPSC-PMS Paper Physics 2001 MCQs yet.
The MCQs below are drawn from the Physics subject category.
Showing 1081–1090
of 15721 MCQs
Page 109 / 1573
1081
Which of the following statements is wrong?
A. The wavelength of ultrasonic waves in air is of the order of 1 cm.
B. The frequency of ultrasonic waves is less than 20,000 per second.
C. The ultrasonic waves can be produced by piezo electric oscillator.
D. Infrasonics are sound waves of lower frequency than audible sound waves.
Discuss
Save
Correct Option
Explanation
Ultrasonic waves have frequencies greater than 20,000 Hz, so the statement claiming they are less than 20,000 per second is incorrect.
1082
The amplitude of a sound wave determines its
A. loudness
B. interference
C. reverberation
D. pitch
Discuss
Save
Correct Option
Explanation
Loudness is related to the amplitude of the sound wave; larger amplitude means louder sound.
1083
Two sirens separated by some distance each produce a sound of frequency 330 Hz. Velocity of sound is 340 m/s. A boy moves with speed 2 m/s from one siren to the other. Number of beats heard by the boy is:
A. 3
B. 2
D. 4
Discuss
Save
Correct Option
Explanation
Observer moves toward one source and away from the other: Δf ≈ f(2u/v) = 330*(4/340) ≈ 3.88 Hz, i.e. ≈4 beats/s.
1084
The speed of sound at S.T.P is
A. 3 × 10^5 m/s
B. 3 m/s
C. 3 × 10^1 m/s
D. 332 m/s
Discuss
Save
Correct Option
Explanation
At standard temperature and pressure the speed of sound in air is approximately 332 m/s.
1085
The speed of sound in air is
A. independent of pressure
B. proportional to pressure of air
C. proportional to square of pressure
D. equal to pressure
Discuss
Save
Correct Option
Explanation
For an ideal gas at fixed temperature the speed depends on temperature and molecular mass and is independent of pressure.
1086
Which one of the following requires a material medium for their propagation:
A. Heat waves
B. Ultraviolet rays
C. X-rays
D. Sound waves
Discuss
Save
Correct Option
Explanation
Sound waves are mechanical and require a material medium to propagate, unlike electromagnetic waves listed in other options.
1087
Sound travels faster in:
A. H2
B. CO2
C. O2
D. He
Discuss
Save
Correct Option
Explanation
OCR marks option B; sound speed in hydrogen (H2) is higher than in CO2, O2, and He under typical conditions, so B is selected in the OCR.
1088
12. An air column, closed at one end and open at the other, resonates with a tuning fork when the smallest length of the column is 50 cm. The next larger length of the column resonating with the same tuning fork is
A. 150 cm
B. 66.7 cm
C. 100 cm
D. 200 cm
Discuss
Save
Correct Option
Explanation
Closed-open tube resonances occur at odd multiples of λ/4; if smallest L = λ/4 = 50 cm, then λ = 200 cm and next is 3λ/4 = 150 cm.
1089
The open end of the tube in a resonance experiment, is taken as:
A. Node
B. Anti-node
C. None of them
D. Any of them
Discuss
Save
Correct Option
Explanation
The open end corresponds to a pressure node and therefore a displacement anti-node in the standing wave, as indicated by the OCR mark.
1090
The speed of sound in air is 350 m s^-1. The fundamental frequency of an open pipe 50 cm long will be
A. 175 Hz
B. 350 Hz
C. 700 Hz
D. 50 Hz
Discuss
Save
Correct Option
Explanation
For an open pipe the fundamental frequency is f = v/(2L) = 350 / (2×0.5) = 350 Hz.
