WAVE MOTION QUIZ-5

Q1. The frequency of tuning forks A and B are respectively 3% more and 2% less than the frequency of tuning fork C. When A and B are simultaneously excited, 5 beats per second are produced. Then the frequency of the tuning fork 'A' in (in Hz) is

•  98
•  100
•  105
•  103

Solution

Q2.In a stationary wave all the particles

•  On either side of a node vibrate in same phase
•  In the region between two nodes vibrate in same phase9
•  In the region between two antinodes vibrate in same phase
•  Of the medium vibrate in same phase

Solution
In stationary wave all the particles in one particular segment (i.e., between two nodes) vibrates in the same phase

Q3.  A standing wave having 3 nodes and 2 antinodes is formed between two atoms having a distance 1.21 Å between them. The wavelength of the standing wave is

•   1.21Å
•  1.42Å
•  6.05Å
•  3.63Å

Solution

Q4. 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 30°, then the angle of refraction will be

•  45°
•  30°
•  60°
•  90°

Solution

Q5.When both the listener and source are moving towards each other, then which of the following is true regarding frequency and wavelength of wave observed by the observer?

•  More frequency, less wavelength
•  More frequency, more wavelength
•  less frequency, less wavelength
•  More frequency, more wavelength

Solution
 

Q6. The fundamental frequency of a sonameter wire is v. if its radius is doubled and its tension becomes half, the material of the wire remains same, the new fundamental frequency will be

•  V
•  v/(2√2)
• v/2
•  v/√2

Solution

Q7.Beats are produced by two travelling waves each of loudness I and nearly equal frequencies n_1and n_2. The beat frequency will be …. and maximum loudness hard will be

•  (n_1-n_2 ),2I
•  (n_1-n_2 ),I
•  (n_1-n_2 ),4I
•  (n_1-n_2 ),3I

Solution
Beat frequency=number of beats s^(-1) =n_1-n_2 And maximum loudness =(a+a)^2=4a^2=4I_1 or 4I_2=4I

Q8.A pulse of a wave train travels along a stretched string and reaches the fixed end of the string. It will be reflected with

•  The same phase as the incident pulse with no reversal of velocity
•  A phase change of 180° with no reversal of velocity
•  A phase change of 180° with velocity reversed
•  The same phase as the incident pulse but with velocity reversed

Solution
A pulse of a wave train when travels along a stretched string and reaches the fixed end of the string, then it will be reflected back to the same medium and the reflected ray suffers a phase change of π with the incident wave but wave velocity after reflection does not change.

Q9.A progressive wave y=a sin [(kx-ωt)] is reflected by a rigid wall at x=0. Then the reflected wave can be represented by

•  y=-a sin (kx-ωt)
•  y=a sin (kx-ωt)
•  y=a sin (kx+ωt)
•  y=-a sin (kx+ωt)

Solution
Given, Progressive wave y=a sin (kx-ωt) When reflected by right wall Progressive wave y’= a sin [k(-x)-wt)] Or y’ = a sin [-(kx+ωt)] Or y’ = a sin (kx+ωt)

Q10. If the temperature is raised by 1 K from 300 K the percentage change in the speed of sound in the gaseous mixture is (R=8.31 J/mol-K)

•  0.334%
•  0.167%
•  1%
• 2%

Solution