The frequency of the fundamental note in a wire stretched under tension T is v. If the tension is increased to 25 T, then the frequency of the fundamental note will be a) 25f b) 5f c) 10f d) f Answer: b) 5f Solution: The fundamental frequency f = (1/2L) √(T/m) (f'/f)... View Article
A transverse wave propagating on a stretched string of linear density 3 × 10-4 kg-m-1 is represented by the equation, y = 0.2 sin (1.5x + 60t ), where, x is in metre and t is in second. The tension in the string (in newton) is a) 0.24 b) 0.48 c) 1.20 d) 1.80 Answer: b) 0.48 Solution: y = 0.2 sin (1.5x + 60t ) Comparing with standard... View Article
Two closed organ pipe A and B have the same length. A is wider than B. They resonate in the fundamental mode at frequencies vA and vB respectively, then a) vA = vB b) vA > vB c) vA < vB d) either (2) or (3) depending on the ratio of their diameters Answer: c) vA < vB Solution: In... View Article
In an experiment with a sonometer, a tuning fork of frequency 256 Hz resonates with a length of 25 cm and another tuning fork resonates with a length of 16 cm. The tension of the string remains constant. The frequency of the second tuning fork is a) 163.84 Hz b) 400 Hz c) 320 Hz d) 204.8 Hz Answer: b) 400 Hz Solution: F = (1/2L) √(T/m) F ∝ (1/L) F... View Article
In Melde’s experiment in the transverse mode, the frequency of the tuning fork and the frequency of the waves in the string are in the ratio a) 2 : 1 b) 4 : 1 c) 1 : 1 d) 1 : 2 Answer: 1:1 Solution: The tuning fork and the string are in resonance So, their frequencies are equal... View Article
A segment of wire vibrates with a fundamental frequency of 450 Hz under a tension of 9 kg–wt. Then, tension at which the fundamental frequency of the same wire becomes 900 Hz is a) 36 kg–wt b) 27 kg–wt c) 18 kg–wt d) 72 kg–wt Answer: a) 36 kg–wt Solution: Frequency,... View Article
A wave has velocity v in medium P and velocity 2v in medium Q. If the wave is incident in medium P at an angle of 300, then the angle of refraction will be a) 300 b) 450 c) 600 d) 900 Answer: d) 900 Solution: Given, A wave has velocity v in medium P and velocity 2v in medium Q... View Article
Two periodic waves of intensities I1 and I2 pass through a region at the same time in the same direction. The sum of the maximum and minimum intensities is a) I1 + I2 b)(√I1 +√I2)2 c) (√I1 - √I2)2 d) 2(I1 + I2) Answer: d) 2(I1 + I2) If two... View Article
When both the listener and source are moving towards each other, then which of the following is true regarding frequency and wavelength of the wave observed by the observer? a) More frequency, less wavelength b) More frequency, more wavelength c) Less frequency, less wavelength d) More frequency, constant... View Article
Radar waves are sent towards a moving aeroplane and the reflected waves are received. When the aeroplane is moving towards the radar, the wavelength of the wave a) decreases b) increases c) remains the same d) sometimes increases or decreases Answer: a) decreases Solution: When an... View Article
The extension in a string obeying Hooke’s law is x. The speed of sound in the stretched string is v. If the extension in the string is increased to 1.5 x, the speed of sound will be a) 1.22 v b) 0.61 v c) 1.50 v d) 0.75 v Answer: a) 1.22 v Solution: Velocity of sound by a stretched string, v =... View Article
A glass tube of length 1.0 m is completely filled with water. A vibrating tuning fork of frequency 500 Hz is kept over the mouth of the tube and the water is drained out slowly at the bottom of the tube. If the velocity of sound in air is 330 ms -1, then the total number of resonances, that occur will be a) 2 b) 3 c) 1 d) 5 Answer: b) 3 Solution: f=v/4l ⇒ l=v/4f Therefore, l1=v/4f1 =330/(4×500) =0.165m... View Article
While measuring the speed of sound by performing a resonance column experiment, a student gets the first resonance condition at a column length of 18 cm during winter. Repeating the same experiment during summer, she measures the column length to be x cm for the second resonance. Then a) 18 > x b) x > 54 c) 54 > x > 36 d) 36 > x >18 Answer: b) x > 54 Solution: For the first... View Article
If the equation of transverse wave is y = 2sin (kx – 2t ), then the maximum particle velocity is a) 4 unit b) 2 unit c) zero d) 6 unit Answer: a) 4 unit Solution: Given, y=2sin(kx−2t) Comparing with the standard... View Article
Two points on a travelling wave having frequency 600 Hz and velocity 300 ms-1 are 60° out of phase, then the minimum distance between the two points is a) 0.3 b) 0.17 c) 0.25 d) 0.4 Answer: b) 0.17 Solution: Velocity(V)= frequency(f) x wavelength(λ) λ = V/f = 300/600 =... View Article
The equation of a progressive wave is given by y =20 sin (600πt – 0.02πx). The frequency of the wave is a) 330 Hz b) 342 Hz c) 365 Hz d) 660 Hz Answer: a) 330 Hz Solution: y=15 sin (660πt−0.02πx) Comparing with the... View Article
The speed of sound in gas of density ρ at a pressure p is proportional to a) (p/ρ)2 b)(p/ρ)3/2 c) √(ρ/p) d) √(p/ρ) e) (ρ/p)2 Answer: c) √(ρ/p) Solution: The speed of the sound, v = √(γp/ρ) v ∝ √(p/ρ) p =... View Article
If a sound absorber attenuates the sound level by 20 dB. The factor by which the intensity decreases is a) 1000 b) 10000 c) 10 d) 100 Answer: d) 100 Solution: Let the intensity of sound be l and l' Loudness of sound initially... View Article
A stationary point source of sound emits sound uniformly in all directions in a non-absorbing medium. Two points P and Q are at a distance of 4 m and 9 m respectively from the source The ratio of amplitudes of the waves at P and Q is a) 3/2 b) 4/9 c) 2/3 d) 9/4 Answer: 9/4 Solution: For an isotropic point source... View Article
In a 12 – storey house ten people enter a lift cabin. It is known that they will leave the lift in pre-decided groups of 2, 3 and 5 people at different storeys. The number of ways they can do so if the lift does not stop at the second storey is (a) 78 (b) 112 (c) 720 (d) 132 Solution: Leaving the ground floor and the second floor, there are 10 floors in which... View Article
