#### 11th Standard Physics Waves English Medium Free Online Test One Mark Questions with Answer Key 2020 - 2021

11th Standard

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Physics

Time : 00:20:00 Hrs
Total Marks : 20
20 x 1 = 20
1. A uniform rope having mass m hangs vertically from a rigid support. A transverse wave pulse is produced at the lower end. Which of the following plots shows the correct variation of speed v with height h from the lower end?

(a)

(b)

(c)

(d)

2. With propagation of longitudinal waves through a medium, the quantity transmitted is

(a)

matter

(b)

energy

(c)

energy and matter

(d)

energy, matter and momentum

3. The speed ofsound in oxygen (O2) at a certain temp is 460 ms-1 the speed of sound in helium at the same temperature will be

(a)

460 ms-1

(b)

500 ms-1

(c)

650 ms-1

(d)

1420 ms-1

4. The ratio of the velocity of sound in a monatomic gas to that in a triatomic gas having same molar mass, under similar conditions of temperature and pressure, is _________.

(a)

1.12

(b)

1.25

(c)

1.50

(d)

1.6

5. The path difference between the two waves Y1 = a1 sin $\left( \omega t-\frac { 2\pi x }{ \lambda } \right)$ and Y2 = a2 cos$\left( \omega t-\frac { 2\pi x }{ \lambda } +\phi \right)$is _________.

(a)

$\frac { \lambda }{ 2\pi } \phi \quad$

(b)

$\frac { \lambda }{ 2\pi } \left( \phi +\frac { \pi }{ 2 } \right)$

(c)

$\frac { 2\pi }{ \lambda } \left( \phi +\frac { \pi }{ 2 } \right)$

(d)

$\frac { 2\pi }{ \lambda } \phi$

6. the velocity of sound in air is 340 ms-1, a person singing a note of frequency 250 cps is producing sound waves with a wavelength of ________

(a)

0.7

(b)

1.36 cm

(c)

1.36 m

(d)

85 km

7. The Doppler effect is applicable for ________.

(a)

light waves

(b)

sound waves

(c)

space waves

(d)

both (a) and (b)

8. Sound waves of wavelength greater than that of audible sound are called _______.

(a)

infrasonic waves

(b)

ultrasonic waves

(c)

sonic waves

(d)

seismic waves

9. A transverse wave propagating along x-axis is represented by y)x,t)=8.0sin $\left( 0.5\pi x-4\pi -\frac { \pi }{ 2 } \right)$ where x is in metres and t is in seconds. The speed of the wave is _________.

(a)

0.5m/s

(b)

$\frac{\pi}{4}$m/s

(c)

8 m/s

(d)

4π m/s

10. Doppler effect in sound is due to _________.

(a)

motion of source

(b)

motion of observer

(c)

relative motion of source and observer

(d)

none of the above

11. A source of sounds emiting waves of frequency 100 Hz and an observer 0 are located at same distance from each other The source is moving with a speed of 19.4 ms-1 at an angle of 60° with the source-observer line as shown in the figure. The observer is at rest. The apparent frequency observed by the observer (velocity of sound in air 330 ms-1) is

(a)

97 Hz

(b)

100 Hz

(c)

103 Hz

(d)

106 Hz

12. A vibrating stretched string resonates with a tuning fork of frequency 512 Hz when the length of the string is 0.5 m. The length of the string required to vibrate resonantly with a tuning fork of frequency 256 Hz would be _________.

(a)

0.25 m

(b)

0.75 m

(c)

1.0 m

(d)

2.0 m

13. sonometer wire is vibrating in the second overtone. In the wire there are _______.

(a)

two nodes and two antinodes

(b)

one node and two antinodes

(c)

four nodes and three antinodes

(d)

three nodes and three antinodes

14. A standing wave is represented by y =A sin (100t) cos (0.01x) where y and A are in millimetres, t in seconds and x in metres. The velocity of the wave is __________.

(a)

104 m/s

(b)

1 m/s

(c)

10-4 m/s

(d)

not derivable from the above information

15. Two waves of the same frequency and intensity superimpose with each other in opposite phases. Then after superposition the __________.

(a)

intensity increases to four times

(b)

intensity increase to two times

(c)

frequency increases to four times

(d)

none of the above

16. An air column in a pipe, which is closed at one end, will be in resonance with a vibrating tuning fork of frequency 256 Hz, .if the length of the column in centimeter is (velocity of sound in air = 340 m/s)

(a)

21.25

(b)

125

(c)

62.50

(d)

33.2

17. Two sound waves with wavelengths 5.0 cm and 5.5 cm, respectively each propagate in a gas with velocity 330 m/s. The number of beats per second will be _______

(a)

0

(b)

1

(c)

6

(d)

12

18. A closes organ pipe of length 20 cm is sounded with a tuning fork in resonance. What is the frequency of the tuning fork? (v = 332 m/s)________

(a)

300 Hz

(b)

350 Hz

(c)

375 Hz

(d)

415 Hz

19. In a resonance tube, the first resonance is obtained at 40 em length, using a tuning fork of frequency 450 Hz. Ignoring end correction, the velocity of sound in air is __________

(a)

620 m/s

(b)

720 m/s

(c)

820 m/s

(d)

1020 m/s

20. The fundamental frequency of a closes organ pipe of length 20 cm is equal to the second overtone of an organ pipe open at both the ends. The length of the organ pipe open at both the ends is __________.

(a)

80 cm

(b)

100 cm

(c)

120 cm

(d)

140 cm