Two Cu wires of radii R1 and R2 are such that (R1>R2). Then which of the following is true?
(a) Transverse wave travels faster in thicker wire (b) Transverse wave travels faster in thinner wire (c) Travels with the... View Article
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When two waves of almost equal frequencies v1 and v2 reach at point simultaneously, the time interval between successive maxima is
(a) v1 – v2 (b) v1 + v2 (c) 1/(v1+v2) (d) 1/(v1-v2) Solution: (d) 1/(v1-v2) When two waves of almost... View Article
Which quantity is transmitted with propagation of longitudinal waves through a medium?
(a) matter (b) energy (c) energy and matter (d) frequency Solution: (b) energy Longitudinal waves are propagated by propagation of... View Article
A wave represented by the equation y = a cos (kx – ωt) is superposed with another wave to form a stationary wave such that point x = 0 is a node. The equation for the other wave is
(a) a sin(kx+ωt) (b) −a cos(kx−ωt) (c) −a cos(kx+ωt) (d) −a sin(kx−ωt) Solution: (c) −a cos(kx+ωt) Let us consider y... View Article
An observer is moving with half the speed of light towards a stationary microwave source emitting waves at frequency10 GHz. What is the frequency of the microwave measured by the observer?
(a) 17.3 GHz (b) 15.3 GHz (c) 10.1 GHz (d) 12.1 GHz Solution Doppler effect in light (speed of observer... View Article
Two stereo speakers are separated by a distance of 2.40 m. A person stands at a distance of 3.20 m directly in front of one of the speakers
Question: Two stereo speakers are separated by a distance of 2.40 m. A person stands at a distance of 3.20... View Article
A source S and a detector D are placed at a distance d apart. A big cardboard is placed at a distance √2 d from the source and the detector
Question: A source S and a detector D are placed at a distance d apart. A big cardboard is placed... View Article
A source of sound S and a detector D are placed at some distance from one another. A big cardboard is placed near the detector
Question: A source of sound S and a detector D are placed at some distance from one another. A big... View Article
Two audio speakers are kept some distance apart and are driven by the same amplifier system. A person is sitting at a place 6.0 m from one of the speakers and 64 in from the other. If the sound signal is continuously varied from 500 Hz to 5000 Hz, what are the frequencies for which there is a destructive interference at the place of the listener? Speed of sound in air = 320 m/s.
The path difference of the two sound waves is: ΔL = 6.4 – 6.0 = 0.4 m The wavelength of... View Article
In Quincke’s experiment, the sound intensity has a minimum value I at a particular position. As the sliding tube is pulled out by a distance of 16.5 mm, the intensity increases to a maximum of 9I. Take the speed of sound in air to be 330 m/s.
(a) Find the frequency of the sound source. (b) Find the ratio of the amplitudes of the two waves arriving... View Article
In Quincke’s experiment the sound detected is changed from a maximum to a minimum when the sliding tube is moved through a distance of 2.50 cm. Find the frequency of sound if the speed of sound in air is 340 m s-1.
Distance between maximum and minimum: λ/4 = 2.50 cm => λ = 2.50 x 4 = 10 cm = 10-1... View Article
The noise level in a classroom in absence of the teacher is 50 dB when 50 students are present. Assuming that on the average each student outputs same sound energy per second, what will be the noise level if the number of students is increased to 100?
β A = 10 log10 (50I/lo) and β B = 10 log10 (100 I/lo) Where, lo is constant reference intensity... View Article
If the sound level in a room is increased from 50 dB to 60 dB, by what factor is the pressure amplitude increased?
Constant reference intensity = Io = 10-12 W/m2 The initial intensity is: β1 = 10 log10 (l1/lo) Where, lo is... View Article
Sound with intensity larger than 120 dB appears painful to a person. A small speaker delivers 2.0 W of audio output. How close can the person get to the speaker without hurting his ears?
If sound level = 120 dB then l = intensity = 1 W/m2 Audio output = 2W (given) Let x... View Article
If the intensity of sound is doubled, by how many decibels does the sound level increase?
Sound level β1: β1 = 10 log10 (l/lo) Where, lo is constant reference intensity When the intensity doubles, the sound... View Article
The sound level at a point 5.0 m away from a point source is 40 dB. What will be the level at a point 50 m away from the source?
Sound level = β = 10 log10 (l/lo) As per given statement, βA = 10 log10 (lA/lo) => lA/lo =... View Article
The intensity of sound from a point source is 1.0 × 10-8 W m-2 at a distance of 5.0 m from the source. What will be the intensity at a distance of 25 m from the source?
Here l1 = 1 x 10-8 W m-2 r1 = 5 m and r2 = 25 m l2 =? We... View Article
A source of sound operates at 20 kHz, 20 W emitting sound uniformly in all directions. The speed of sound in air is 340 m s-1 and the density of air is 1.2 kg m-3.
(a) What is the intensity at a distance of 60 m from the source? (b) What will be the pressure... View Article
Calculate the bulk modulus of air from the following data about a sound wave of wavelength 35 cm travelling in air. The pressure at a point varies between (1.0 × 105 ± 14) pa and the particles of the air vibrate in simple harmonic motion of amplitude 5.5 × 10-6 m.
Wavelength of sound wave = λ = 35 cm = 35 x 10-2 m Pressure amplitude = po = (1... View Article
Find the change in the volume of 1.0 liter kerosene when it is subjected to an extra pressure of 2.0 × 105 N m-2 from the following data. Density of kerosene = 800 kg m-3 and speed of sound in kerosene 1330 m s-1.
The velocity in terms of the bulk modulus and density : v = √(k/p) where, k = v2 ρ =>... View Article
