#### Waves Model Question Paper

11th Standard

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Physics

Time : 02:00:00 Hrs
Total Marks : 60
7 x 1 = 7
1. A student tunes his guitar by striking a 120 Hertz with a tuning fork, and simultaneously plays the 4th string on his guitar. By keen observation, he hears the amplitude of the combined sound oscillating thrice per second. Which of the following frequencies is the most likely the frequency of the 4th string on his guitar?.

(a)

130

(b)

117

(c)

110

(d)

120

2. For a particular tube, among six harmonic frequencies below 1000 Hz, only four harmonic frequencies are given: 300 Hz, 600 Hz, 750 Hz and 900 Hz. What are the two other frequencies missing from this list?.

(a)

100 Hz, 150 Hz

(b)

150 Hz, 450 Hz

(c)

450 Hz, 700 Hz

(d)

700 Hz, 800 Hz

3. A sound wave whose frequency is 5000 Hz travels in air and then hits the water surface. The ratio of its wavelengths in water and air is

(a)

4.30

(b)

0.23

(c)

5.30

(d)

1.23

4. The displacement y of a wave travelling in the x direction is given by y= (2 x10 -3) sin (300t -2x+$\frac{\pi}{4}$), where x and y are measured in metres and t in second. The speed of the wave is

(a)

150 ms-1

(b)

300 ms-1

(c)

450 ms-1

(d)

600 ms-1

5. Which of the following represents a wave

(a)

(x - vt)3

(b)

x(x+vt)

(c)

$\frac{1}{x+vt}$

(d)

sin(x+vt)

6. 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

7. Length of a string tied to two rigid supports is 40 cm maximum length of a stationary wave produced on it is

(a)

20

(b)

80

(c)

40

(d)

120

8. 10 x 2 = 20
9. The average range of frequencies at which human beings can hear sound waves varies from 20 Hz to 20 kHz. Calculate the wavelength of the sound wave in these limits. (Assume the speed of sound to be 340 m s-1.

10. Sketch y = x −a for different values of a.

11. What is meant by waves?.

12. Define wavelength.

13. Explain Doppler Effect.

14. What is meant by an echo?. Explain.

15. Why is it that transverse waves cannot be produced in a gas?. Can the transverse waves can be produced insolids and liquids?

16. How do animals sense impending danger of hurricane?

17. What is Echo?

18. What is Reverberation?

19. 6 x 3 = 18
20. Consider a string whose one end is attached to a wall. Then compute the following in both situations given in figure (assume waves crosses the distance in one second)
(a) Wavelength, (b) Frequency and
(c) Velocity

21. Calculate the speed of sound in a steel rod whose Young’s modulus Y = 2 × 1011 N m-2 and $\rho$ = 7800 kg m-3.

22. Write the characteristics of wave motion.

23. Distinguish between transverse and longitudinal waves.

24. Write a not about Stethoscope.

25. Derive the relation between Intensity and loudness

26. 3 x 5 = 15
27. Two speakers C and E are placed 5 m apart and are driven by the same source. Let a man stand at A which is 10 m away from the mid point O of C and E. The man walks towards the point O which is at 1 m (parallel to OC) as shown in the figure. He receives the first minimum in sound intensity at B. Then calculate the frequency of the source. (Assume speed of sound = 343 m s-1)

28. Briefly explain the concept of superposition principle.

29. What is a sonometer?. Give its construction and working. Explain how to determine the frequency of tuning fork using sonometer.