Important Questions For Class 11 Physics Chapter 15- Waves

1. Explosions on other planets are not heard on earth. Why? [1]

2. Why longitudinal waves are called pressure waves? [1]

3. Why do tuning forks have two prongs? [1]

4. A pipe 20 cm long is closed at one end. Which harmonic mode of the pipe is resonantly excited by a 430 Hz source? Will this source be in resonance with the pipe if both the ends are open?
[2]

5. Can beats be produced in two light sources of nearly equal frequencies? [2]

6. A person deep inside water cannot hear sound waves produces in air. Why? [2]

7. If the splash is heard 4.23 seconds after a stone is dropped into a well. 78.4
metes deep, find the velocity of sound in air? [2]

8. How roar of a lion can be differentiated from bucking of a mosquito? [2]

9. Explain briefly the analytical method of formation of beats? [3]

10. Give two cases in which there is no Doppler effect in sound? [2]

11. The length of a sonometer wire between two fixed ends is 110cm. Where the two bridges should be placed so as to divide the wire into three segments whose fundamental frequencies are in the ratio of 1:2:3?

12. Velocity of sound increases on a cloudy day. Why? [1]

13. Sound of maximum intensity is heard successively at an interval of 0.2 second on sounding two tuning fork to gather. What is the difference of frequencies of two tuning forks? [1]

14. If two sound waves has a phase difference of 600, then find out the path difference between the two waves? [1]

15. If string wires of same material of length l and 2l vibrate with frequencies 100HZ and 150 HZ. Find the ratio of their frequencies? [2]

16. Two similar sonometer wires of the same material produces 2 beats per second. The length of one is 50cm and that of the other is 50.1 cm. Calculate the frequencies of two wives? [2]

17. Why are all stringed instruments provided with hollow boxes? [2]

18. A Tuning fork of frequency 300HZ resonates with an air column closed at one end at 27 C. How many beats will be heard in the vibration of the fork and the air column at 0 C? [2]

19. A vehicle with horn of frequency ‘n’ is moving with a velocity of 30m/s in a direction perpendicular to the straight line joining the observer and the vehicle. If the observer perceives the sound to have a frequency of n+n1. Calculate n1? [2]

20. We cannot hear echo in a room. Explain? [2]

21. Show that the frequency of nth harmonic mode in a vibrating string which is closed at both the end is ‘n’ times the frequency of the first harmonic mode?

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