WAVE MOTION QUIZ-3

Q1. A cylindrical tube containing air is open at both ends. If the shortest length of the tube for resonance with a given fork is 2 cm, the next shortest length for resonance with the same fork will be

•  80 cm
•  90 cm
•  60 cm
•  40 cm

Solution
As the tube is open at both ends, therefore, next shortest length for resonance =2×20=40 cm

Q2.On which principle does sonometer works?

•  Hooke’s law
•  Resonance
•  Newton’s law
•  Elasticity

Solution
Sonometer works on the principle of resonance. At resonance the wire of sonometer vibrate with maximum amplitude.

Q3.  The intensity ratio of two waves is 1:9. The ratio of their amplitudes, is

•   3:1
•  9:1
•  1:9
•  1:3

Solution

Q4. The driver of a car travelling with speed 30 metres per second towards a hill sounds a horn of frequency 600 Hz. If the velocity of sound in air is 330 metres per second, the frequency of the reflected sound as heard by the driver is

•  500 Hz
•  550 Hz
•  555.5 Hz
•  720 Hz

Solution

Q5.The musical interval between two tones of frequencies 320 Hz and 240 Hz is

•  (4/3)
•  560
•  320×240
•  80

Solution
 Musical interval is the ratio of frequencies =320/240=4/3

Q6. Two tuning fork, A and B produce notes of frequencies 258 Hz and 262 Hz. An unknown note sounded with a produces certain beats. When the same note is sounded with B, the beat frequency gets doubled, the unknown frequency is

•  280 Hz
•  254 Hz
• 256 Hz
•  300 Hz

Solution

Q7.The amplitude of two waves are in ratio 5:2. If all other conditions for the two waves Are same, then what is the ratio of their energy densities?

•  5:2
•  5:4
•  25:4
•  4:5

Solution

Q8.v_1 and v_2 are the velocities of sound at the same temperature in two monoatomic gases of densities ρ_1 and ρ_2 respectively. If ρ_1/ρ_2=1/4 then the ratio of velocities v_1 and v_2 will be

•  1∶2
•  2∶1
•  1∶4
•  4∶1

Solution

Q9.The equation y=A cos^2⁡〖(2π nt-2π x/λ)〗 represents a wave with

•  Amplitude A, frequency n and wavelength λ
•  Amplitude A, frequency 2n and wavelength 2λ
•  Amplitude A/2, frequency 2n and wavelength λ
•  Amplitude A/2, frequency 2n and wavelength λ/2

Solution

Q10. A wavelength 0.60 cm is produced in air and it travels at a speed of 300 ms^(-1). It will be an

•  Infrasonic wave
•  Ultrasonic wave
•  Audible wave
• None of the above

Solution
n=v/λ=300/(0.6×〖10〗^(-2) ) Hz=3/6×〖10〗^4 Hz=50,000Hz ⇒ Wave is ultrasonic