Tiêu đề 16. Waves and Sound Easy.pdf ✅

1. Which of the following statements is wrong (a) Sound travels in straight line (b) Sound is a form of energy (c) Sound travels in the form of waves (d) Sound travels faster in vacuum than in air 2. The relation between frequency ‘n’ wavelength ‘’ and velocity of propagation ‘v’ of wave is (a) n = v (b) n =  / v (c) n = v /  (d) n = 1 / v 3. Ultrasonic, Infrasonic and audible waves travel through a medium with speeds Vu Vi , and Va respectively, then (a) Vu Vi , and Va are nearly equal (b) Vu  Va  Vi (c) Vu  Va  Vi (d) Va  Vu and Vu  Vi 4. The distance between two consecutive crests in a wave train produced in a string is 5 cm. If 2 complete waves pass through any point per second, the velocity of the wave is (a) 10 cm/sec (b) 2.5 cm/sec (c) 5 cm/sec (d) 15 cm/sec 5. A tuning fork makes 256 vibrations per second in air. When the velocity of sound is 330 m/s, then wavelength of the tone emitted is (a) 0.56 m (b) 0.89 m (c) 1.11 m (d) 1.29 m 6. A man sets his watch by a whistle that is 2 km away. How much will his watch be in error. (speed of sound in air 330 m/sec) (a) 3 seconds fast (b) 3 seconds slow (c) 6 seconds fast (d) 6 seconds slow 7. When a sound wave of frequency 300 Hz passes through a medium the maximum displacement of a particle of the medium is 0.1 cm. The maximum velocity of the particle is equal to (a) 60  cm/sec (b) 30  cm/sec (c) 30 cm/sec (d) 60 cm/sec 8. Sound waves have the following frequencies that are audible to human beings (a) 5 c/s (b) 27000 c/s (c) 5000 c/s (d) 50,000 c/s 9. Velocity of sound waves in air is 330 m/sec. For a particular sound in air, a path difference of 40 cm is equivalent to a phase difference of 1.6 . The frequency of this wave is (a) 165 Hz (b) 150 Hz (c) 660 Hz (d) 330 Hz 10. The wavelength of ultrasonic waves in air is of the order of
(a) 5 5 10−  cm (b) 8 5 10−  cm (c) 5 5 10  cm (d) 8 5 10  cm 11. The relation between phase difference () and path difference (x) is (a) 2 x     =  (b)  =    2 x (c) 2 x   =   (d) 2 x     = 12. A hospital uses an ultrasonic scanner to locate tumors in a tissue. The operating frequency of the scanner is 4.2 MHz. The speed of sound in a tissue is 1.7 km-s –1 . The wavelength of sound in the tissue is close to (a) 4 4 10−  m (b) 3 8 10−  m (c) 3 4 10−  m (d) 4 8 10−  m 13. The minimum audible wavelength at room temperature is about (a) 0.2 Å (b) 5 Å (c) 5 cm to 2 metre (d) 20 mm 14. The ratio of the speed of sound in nitrogen gas to that in helium gas, at 300 K is (a) 2 / 7 (b) 1 /7 (c) 3 / 5 (d) 6 / 5 15. In a sinusoidal wave, the time required for a particular point to move from maximum displacement to zero displacement is 0.170 second. The frequency of the wave is (a) 1.47 Hz (b) 0.36 Hz (c) 0.73 Hz (d) 2.94 Hz 16. The number of waves contained in unit length of the medium is called (a) Elastic wave (b) Wave number (c) Wave pulse (d) Electromagnetic wave 17. The frequency of a rod is 200 Hz. If the velocity of sound in air is 1 340 − ms , the wavelength of the sound produced is (a) 1.7 cm (b) 6.8 cm (c) 1.7 m (d) 6.8 m 18. Frequency range of the audible sounds is (a) 0 Hz – 30 Hz
(b) 20 Hz – 20 kHz (c) 20 kHz – 20,000 kHz (d) 20 kHz – 20 MHz 19. In a medium sound travels 2 km in 3 sec and in air, it travels 3 km in 10 sec. The ratio of the wavelengths of sound in the two media is (a) 1 : 8 (b) 1 : 18 (c) 8 : 1 (d) 20 : 9 20. A stone is dropped into a lake from a tower 500 metre high. The sound of the splash will be heard by the man approximately after (a) 11.5 seconds (b) 21 seconds (c) 10 seconds (d) 14 seconds 21. When sound waves travel from air to water, which of the following remains constant (a) Velocity (b) Frequency (c) Wavelength (d) All the above 22. A stone is dropped in a well which is 19.6m deep. Echo sound is heard after 2.06 sec (after dropping) then the velocity of sound is (a) 332.6 m/sec (b) 326.7 m/sec (c) 300.4 m/sec (d) 290.5 m/sec 23. At what temperature velocity of sound is double than that of at 0°C (a) 819 K (b) 819°C (c) 600°C (d) 600 K 24. Velocity of sound is maximum in (a) Air (b) Water (c) Vacuum (d) Steel 25. If velocity of sound in a gas is 360 m/s and the distance between a compression and the nearest rarefaction is 1m, then the frequency of sound is (a) 90 Hz (b) 180 Hz (c) 360 Hz (d) 720 Hz 26. If the density of oxygen is 16 times that of hydrogen, what will be the ratio of their corresponding velocities of sound waves (a) 1 : 4 (b) 4 : 1 (c) 16 : 1 (d) 1 : 16 27. At which temperature the speed of sound in hydrogen will be same as that of speed of sound in oxygen at 100oC (a) – 148oC (b) – 212.5oC (c) – 317.5oC
(d) – 249.7oC 28. A tuning fork produces waves in a medium. If the temperature of the medium changes, then which of the following will change (a) Amplitude (b) Frequency (c) Wavelength (d) Time-period 29. The wave length of light in visible part (V ) and for sound (S ) are related as (a)   V S  (b)   S V  (c)   S V = (d) None of these 30. Which of the following is different from others (a) Velocity (b) Wavelength (c) Frequency (d) Amplitude 31. The phase difference between two points separated by 1m in a wave of frequency 120 Hz is o 90 . The wave velocity is (a) 180 m/s (b) 240 m/s (c) 480 m/s (d) 720 m/s 32. The echo of a gun shot is heard 8 sec. after the gun is fired. How far from him is the surface that reflects the sound (velocity of sound in air = 350 m/s) (a) 1400 m (b) 2800 m (c) 700 m (d) 350 m 33. A man sets his watch by the sound of a siren placed at a distance 1 km away. If the velocity of sound is 330 m/s (a) His watch is set 3 sec. faster (b) His watch is set 3 sec. slower (c) His watch is set correctly (d) None of the above 34. Velocity of sound in air is (a) Faster in dry air than in moist air (b) Directly proportional to pressure (c) Directly proportional to temperature (d) Independent of pressure of air 35. Two monoatomic ideal gases 1 and 2 of molecular masses m1 and m2 respectively are enclosed in separate containers kept at the same temperature. The ratio of the speed of sound in gas 1 to that in gas 2 is given by (a) 2 1 m m (b) 1 2 m m (c) 2 1 m m (d) 1 2 m m