Physics Chapter 4 Entry test MCQs
Topic 4
Waves
1. A simple pendulum is attached to the roof of a lift. If the time period of oscillation, when the lift is stationary is T, then the frequency of oscillation when the lift falls freely, will be———–.
a. 1/T
b. Zero
c. Infinity
d. T
2. The length of a simple pendulum executing simple harmonic motion is increased by 21%. The percentage increase in the time period of the pendulum of increased length is?
a. 30%
b. 50%
c. 10.5%
d. 21%
3. If a simple pendulum oscillates with amplitude of 50mm and time period of 2s, then its maximum velocity is?
a. 0.24m/s
b. 0.10m/s
c. 0.32m/s
d. 0.16m/s
4. A spring of force constant k is cut into two pieces, such that one piece is double the length of the other. Then the long piece will have a force constant of
a. 3k
b. (2/3) k
c. 6k
d. (3/2) k
5. The phase difference between the acceleration of a particle executing simple harmonicmotion and the instantaneous velocity is?
a. π/2
b. π
c. 2π
d. 0.707π
6. A siren emitting sound of frequency 800Hz is going away from a static listener with a speed of 30m/s. Frequency of the sound to be heard by the listener is (Take velocity of sound as 330m/s).
a. 481.2Hz
b. 733.3Hz
c. 286.5Hz
d. 644.8Hz
7. Lights can travel in a vacuum but not sound, because——————.
a. Sound waves are electromagnetic in nature
b. Speed of sound is very slow than light
c. Light waves are not electromagnetic in nature
d. Light waves are electromagnetic in nature
8. When sound travels from air to water, which parameter does not change?
a. Velocity
b. Wavelength
c. Temperature
d. Frequency
9. A whistle giving out 450Hz approaches a stationary observer at a speed of 33m/s. The frequency heard by the observer in Hz is (speed of sound = 330m/s).
a. 517
b. 409
c. 500
d. 429
10. A boat at anchor is rocked by waves, whose crests are 100m apart and velocity is 25m/s. The boat bounces up once in every————.
a. 4s
b. 2500s
c. 0.25s
d. 75s
11. The diagram shows a transverse wave at a particular time. The wave is travelling to the right. The frequency of the wave is 12.5Hz.
At the instant shown the displacement is zero at point P. what is the shortest time to elapse before the displacement is zero at point Q.
a. 0.01s
b. 0.03s
c. 0.08s
d. 0.10s
12. In a transverse wave the distance between a crest and a trough is equal to
a. λ
b. λ/2
c. 2λ
d. λ/4
13. If a wave travelling at a speed of 130 m/s and has a wavelength of 5m. Then find out the frequency of the wave?
a. 20 Hz
b. 650 Hz
c. 26 Hz
d. 3.8 x 102 Hz
14. A sinusoidal wave is travelling toward the right as shown. which letter correctly labels the amplitude of the wave?
a. A
b. B
c. D
d. C
15. The sound of lightning flash is heard 3 second after the flash is seen. The distance of the lightning is 1020 metre. The speed of sound is:
a. 332 m/s
b. 340 m/s
c. 1400 m/s
d. none of these
16. When water waves pass from deep water into shallow water how do the frequency, wavelength and speed change.
17. Which of the following waves can be transmitted through solids, liquids and gases?
a. Electromagnetic waves
b. Transverse waves
c. Longitudinal waves
d. Mechanical waves
18. If two sound waves having a phase difference of 60 deg then they will have a path difference of
a. λ/ 3
b. λ/6
c. 3λ
d. λ
19. All the points above the mean position in a rope
a. Compression
b. Crest
c. Rarefaction
d. Trough
20. The distance between consecutive compression and rarefaction in a spring
a. λ / 2
b. λ
c. λ/ 4
d. 2λ.
21. Velocity of sound in vacuum is:
a. 320m s-1
b. 332m s-1
c. 224m s-1
d. Zero
22. Increase in velocity of sound in the air for 1°C rise in temperature is:
a. 61m s-1
b. 1.61m s-1
c. 2m s-1
d. 0.61m s-1
23. The velocity of sound in air would become double than its velocity at 0oC at temperature:
a. 586°C
b. 313°C
c. 1172° C
d. 819 °C
24. Laplace found that the alternate compressions and rarefactions produced in sound waves follow:
a. Adiabatic law
b. Isothermal law
c. Isochoric law
d. All of the above
25. What is added when two waves superimpose?
a. Velocities
b. Amplitude
c. Wavelength
d. None of these