Waves And Sound Test

Result

Waves And Sound Test - 2

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Weekly Quiz Competition

Question 1
1 / -0

A key of a mechanical piano is struck gently and then struck again but much this time. In the second case,

A
sound will be louder but pitch will not be different

B
sound will be louder and pitch will also be higher

C
sound will be louder but pitch will be lower

D
both loudness and pitch will remain unaffected

Solution

Piano is a stringed instrument. When the key is struck harder, the string below it vibrates with higher amplitude, as the intensity of the sound is directly proportional to the square of the amplitude. Hence, sound will be louder. The pitch (frequency) depends upon the tension, length and the mass of the string. Hence, pitch of the sound will remain the same.
Question 2
1 / -0

The speed of sound in humid air is greater than that in dry air because

A
humid air is less dense

B
humid air is dense

C
humid air is elastic

D
humid air is less elastic

Solution

Speed of sound in different media depends upon some inertia factors, such as molecular mass, density and the elasticity of the medium. Since humid air is less dense than dry air, so the speed of sound in humid air is greater than that in dry air.
Question 3
1 / -0

Ultrasonic, infrasonic and audible waves travel through a medium with speeds of v_u, v_i and v_a,respectively. Which of the following relations holds true?

A
v_i = v_a = v_u

B
v_u > v_a > v_i

C
v_u < v_a < v_i

D
v_a ≤ v_u = v

Solution

Velocity of a sound is dependent on the medium. It is independent of the frequency, so v_i = v_a = v_u.
Question 4
1 / -0

What is the change in intensity level when the intensity of a sound increases by a factor of 10⁵?

A
50 dB

B
60 dB

C
70 dB

D
80 dB

Solution

I/I_o= 10⁵
The increase in intensity level is given by:
L = 10 log₁₀(I/I_o) = 10 log₁₀(10⁵)
= 10 × 5 = 50 dB