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Doppler phenomenon is related with

a) pitch (frequency) b) loudness c) quality d) reflection Answer: a) pitch (frequency) Solution: Doppler Effect: When the source... View Article

Two trains, each moving with a velocity of 30 ms ^-1, cross each other. One of the trains gives a whistle whose frequency is 600 Hz. If the speed of sound is 330 ms^-1, the apparent frequency for passengers sitting in the other train before crossing would be

a) 600 Hz b) 630 Hz c) 920 Hz d) 720 Hz Answer: d) 720 Hz Solution: As source and observer are moving towards each other with... View Article

A car sounding its horn at 480 Hz moves towards a high wall at a speed of 20 ms^-1. If the speed of sound is 340 ms ^-1, the frequency of the reflected sound heard by the girl sitting in the car will be closest to

a) 540 Hz b) 524 Hz c) 568 Hz d) 480 Hz Answer: a) 540 Hz Solution: After reflection from the wall, the sound moves towards the... View Article

The change in frequency due to Doppler’s effect does not depend on

a) the speed of the source b) the speed of the observer c) the frequency of the source d) separation between the source and the observer... View Article

A train is approaching with velocity 25 ms ^-1 towards a pedestrian standing on the track, frequency of horn of train is 1 kHz. The frequency heard by the pedestrian is (take, v = 350 ms ^-1 )

a) 1077 Hz b) 1167 Hz c) 985 Hz d) 954 Hz Answer: a) 1077 Hz Solution: Given, v = 350 m/s v = 1 Khz = 1000 vs = 25... View Article

A car is moving with a speed of 72 km–h ^-1 towards a roadside source that emits found at a frequency of 850 Hz. The car driver listens to the sound while approaching the source and again while moving away from the source after crossing it. If the velocity of sound is 340 ms ^-1, the difference between the two frequencies, the driver hears is

a) 50 Hz b) 85 Hz c) 100 Hz d) 150 Hz Answer: c) 100 Hz Solution: By Doppler's Effect When the observer is moving with... View Article

In 1 m long open pipe, what is the harmonic of resonance obtained with a tuning fork of frequency 480 Hz?

a) First b) Second c) Third d) Fourth Answer: c) Third Solution: Frequency of Nth harmonic, n = NV/2l v = speed of sound l =... View Article

Intensity level of sound whose intensity is 10^-8 Wm^-2 is ______ dB

a) 80 dB b) 8 dB c) 4 dB d) 40 dB Answer: d) 40 dB Solution: I = 10-8 Wm-2 Reference intensity I0... View Article

The equation of a simple harmonic wave is given by y = 6sin 2π (2t – 0.1x), where x and y are in mm and t is in second. The phase difference between two particles 2 mm apart at any instant is

a) 18° b) 36° c) 54° d) 72° Answer: d) 72° Solution: Given equation can be written as... View Article

If V_m is the velocity of sound in moist air, V_d is the velocity of sound in dry air, under identical conditions of pressure and temperature

a) Vm < Vd b) Vm > Vd c) VmVd = 1 d) Vm = Vd Answer: b) Vm > Vd Solution: Sound is the vibration of air, so if the... View Article

The ratio of velocity of sound in oxygen to that in hydrogen at same temperature and pressure is approximately

a) 16 : 1 b) 1 : 16 c) 4 : 1 d) 1 : 4 Answer: d) 1 : 4 Solution: Velocity of sound in a gas, v=√γRT/M where... View Article

If sound wave travel from air to water, which of the following remains unchanged?

a) Velocity b) Wavelength c) Frequency d) Intensity Answer: c) Frequency Solution: We know that frequency is independent of... View Article

Compressional wave pulses are sent to the bottom of sea from a ship and the echo is heard after 2 s. If bulk modulus of elasticity of water is 2 × 10⁹ Nm^-2 and mean temperature is 4°C, then the depth of the sea will be

a) 1014 m b) 1414 m c) 2828 m d) 1825 m Answer: b) 1414 m Solution: The speed of sound in water is given by, v = √B/d... View Article

A point source emits sound equally in all directions in a non-absorbing medium. Two points P and Q are at distances of 2m and 3m respectively from the source. The ratio of the intensities of the waves at P and Q is

a) 9 : 4 b) 2 : 3 c) 3 : 2 d) 4 : 9 Answer: a) 9 : 4 Solution: d1 = 2m d2 = 3m Intensity ∝ 1/(distance)2... View Article

Two Cu wires of radii R₁ and R₂, such that (R₁ > R₂ ). Then which of the following is true?

1) Transverse wave travels faster in thicker wire 2) Transverse wave travels faster in thinner wire 3) Travels with the same speed in both... View Article

A string of density 7.5 g cm^-3 and area of cross-section 0.2 mm² is stretched under a tension of 20 N. When it is plucked at the mid-point, the speed of the transverse wave on the wire is

a) 116 ms-1 b) 40 ms-1 c) 200 ms-1 d) 80 ms-1 Answer: a) 116 ms-1 Solution: v = √(T/μ) T = 20 N f = 7.5 g... View Article

A sonometer wire of length 1.5 m is made of steel. The tension in it produces an elastic strain of 1%. What is the fundamental frequency of steel if the density and elasticity of steel are 7.7 × 10³ kg / m³ and 2.2 × 10¹¹ N / m² respectively?

a) 188.5 Hz b) 178.2 Hz c) 200.5 Hz d) 770 Hz Answer: b) 178.2 Hz Solution: Frequency, f = v/2l = (1/2l)√(T/μ)... View Article

A string of mass 3 kg is under the tension of 400 N. The length of the stretched string is 25 cm. If the transverse jerk is stuck at one end of the string, how long does the disturbance take to reach the other end?

a) 0.043 s b) 0.055 s c) 0.034 s d) 0.065 s Answer: a) 0.043 s Solution: L = 25 cm = 25 x 10-2 m M = 3 kg m = M/L =... View Article

Which quantity is transmitted with the propagation of longitudinal waves through a medium?

a) Dispersion b) Energy c) Matter d) Frequency Answer: b) Energy Solution: Energy is transferred with the propagation of the... View Article

A metallic wire of 1 m length has a mass of 10 × 10^-3 kg. If the tension of 100 N is applied to a wire, what is the speed of the transverse wave?

a) 100 m/s b) 10 m/s c) 200 m/s d) 0.1 m/s Answer: a) 100 m/s Solution: length, l = 1 m Mass, M = 10 × 10-3 kg... View Article