NCERT Solutions for Class 11 Physics Physics Part Ii Chapter 15 Waves

Three sound waves of equal amplitudes have frequencies (ν – 1), ν, (ν + 1). They superpose to give beats. The number of beats produced per second will be.

• 4

• 3

• 2

• 1

A wave travelling along the x-axis is described by the equation y(x, t) = 0.005 cos (αx −βt). If the wavelength and the time period of the wave are 0.08 m and 2.0 s, respectively, then α and β in appropriate units are 

• α = 25.00 π, β = π

• α = 0.08/ π,  2.0/π

• α = 0.04 / π , β =1.0/π

• α = 12.50 , β =π/ 2.0

A whistle producing sound waves of frequencies 9500 Hz and above is approaching a stationary person with speed v ms⁻¹. The velocity of sound in air is 300 ms−1. If the person can hear frequencies upto a maximum of 10,000 Hz, the maximum value of v upto which he can hear the whistle is

• 
• 

• 15 ms^-1

• 30 ms^-1

When two tuning forks (fork 1 and fork 2) are sounded simultaneously, 4 beats per second are heard. Now, some tape is attached on the prong of the fork 2. When the tuning forks are sounded again, 6 beats per seconds are heard. If the frequency of fork 1 is 200 Hz, then what was the original frequency of fork 2?

• 200 Hz

• 202 Hz

• 196 Hz

• 204 HN

An observer moves towards a stationary source of the sound, with a velocity one-fifth of the velocity of sound. What is the percentage increase in the apparent frequency?

• 0

• 0.5%

• 5%

• 20%

The displacement y of a particle in a medium can be expressed as y = 10⁻⁶ sin(110t + 20 x + π/4) m, where t is in seconds and x in a meter. The speed of the wave is

• 2000 m/s

• 5 m/s

• 20 m/s

• 5π m/s

The two nearest harmonics of a tube closed at one end and open at other end are 220 Hz and 260 Hz. What is the fundamental frequency of the system?

• 10 Hz

• 20 Hz

• 30 Hz

• 40 Hz

Two soap bubbles coalesce. It is noticed that whilst joined together, the raddii of the bubbles are a and b where a>b. Then the radius of curvature of the interface between the two bubbles will be

• a-b

• a+b

• ab/(a-b)

• ab/(a+b)

A particle is executing the motion x = αcos(ωt-θ).The velocity of the particle is

• αω cosθ

• αω

• αω sinθ

• None of the above

 A particle is executing two different simple harmonic motions, mutually perpendicular, of different amplitudes and having phase difference of $\frac{\mathrm{\pi }}{2}$ The path of the particle will be

• circular

• straight line

• parabolic

• elliptical