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This mock test of Waves MCQ Level - 1 for Physics helps you for every Physics entrance exam.
This contains 10 Multiple Choice Questions for Physics Waves MCQ Level - 1 (mcq) to study with solutions a complete question bank.
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QUESTION: 1

The equation of a wave disturbance is given as :

where X and y are in metres and t in seconds. Choose the wrong statement:

Solution:

y=0.02cos(π/2+50π∗t)cos(10π∗x)

At x=0.3m

y=0.02cos(π/2+50π∗t)cos(3π) = −0.02cos(π/2+50π∗t) (It is right)

Now compare the given equation by the standard stationary wave equation,

y=Acos(ϕ+ω∗t)cos(2π/λ∗x)

2π/λ=10π, λ=0.2m (it is also right)

At x=0.15m,

y=0.02cos(π/2+50π∗t)cos(π/2),

and

v=Aω=0.02∗50π=πms^{−1}

so option d is incorrect.

QUESTION: 2

In a plane progressive harmonic wave particle speed is always less than the wave speed if:

(where A is wavelength of wave)

Solution:

Let equation of a plane progressive harmonic wave be

wave speed

and maximum particle speed

Given that v_{p} < v

The Correct answer is : amplitude of wave is less than

QUESTION: 3

Which of the following is not the standard form of a sine wave?

Solution:

Standard form of a sine wave is

With these substitutions we can see that Equation (1) can be written as options (b).

The correct answer is:

QUESTION: 4

Two sound source are moving in opposite directions with velocities v_{1} and v_{2}(v_{1} > v_{2}). Both are moving away from a stationary observer. The frequency of both the sources is 900 Hz. What is the value of v_{1} - v_{2} so that the beat frequency observed by the observer is 6 Hz. Speed of sound v = 300 mis. Given, that v_{1} and v_{2} « v.

Solution:

The correct answer is: 2 m/s

QUESTION: 5

String 1 has twice the length, twice the radius, twice the tension and twice the density of another string 2. The relation between the fundamental frequencies of 1 and 2 is :

Solution:

(m = mass per unit length =pS)

The correct answer is: f_{2} = 4f_{1}

QUESTION: 6

A string of length L is stretched by L/20 and speed of transverse wave along it is v. The speed of wave when it is stretched by L/10 will be : (assume the Hooke’s law is applicable)

Solution:

The correct answer is: √2v

QUESTION: 7

Speed of transverse wave in a string of density 100 kglm^{3} and area of cross-section 10 mm^{2} under the tension of 10^{3} N is :

Solution:

Here, m = mass per unit length = pS

The correct answer is: 1000 m/s

QUESTION: 8

A wave represented by the equation y1 = Acos(kx- ωt), is superimposed with another wave to form a stationary wave such that the point x = 0 is a node. The equation of the other wave is :

Solution:

y=y_{1} + y_{2}

At x = 0, y = 0 for all values of t only when

The correct answer is:

QUESTION: 9

The frequency changes by 10% as the source approaches a stationary observer with constant speed v_{s}. What would be the percentage change in frequency as the source recedes the observer with the same speed ? Given, that v_{s} « v ( v = speed of sound in air)

Solution:

QUESTION: 10

A heavy rope is suspended from a rigid support. A wave pulse is set up at the lower end, then :

Solution:

Due to weight of the rope, the tension will increase along the rope from the lower end to the upper end. Hence, the pulse will travel with increasing speed as

The correct answer is: the pulse will travel with increasing speed

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