Question

D. Numerical problems
1. A pendulum oscillates 50 times in 6 seconds. Calculate its time period and frequency
2. If the amplitude of vibrations of sound wave is halved, what will be its effect on loudness of sound waves?
3. Sound produced by thunderstorm is heard 10 s after the lightening is seen. Calculate approximate distance of
thunder cloud (speed of sound = 340 m/s).​

Answer 1

Answer:

1. No. of oscillations = 50

Time = 6 s

Frequency = No. of oscillations in 1 second

= 50/6 Hz

= 8.33 Hz

Time period = 1/frequency

= 1/8.33 s

= 0.12 s

2. Loudness is proportional to square of amplitude. So,

If amplitude becomes half, then, loudness will be 1/4 of amplitude.

3. Sound time = 10 s

Speed of sound = 340 m/s

Distance = Speed = Distance/Time

= 340 = D/10

= 3400 m = Distance

Or,

= 3.4 km = Distance

Hope this helps.

Answer 2

$\huge\orange{\overbrace{\red{\underbrace{\color{pink}{{ \red\:{Question}}}}}}}$

2. If the amplitude of vibrations of sound wave is halved, what will be its effect on loudness of sound waves?

$\huge\orange{\overbrace{\red{\underbrace{\color{pink}{{ \red\:{Answer}}}}}}}$

If the amplitude of a sound is halved, its loudness becomes one-fourth.

Loudness depends on the square of the amplitude of the wave.

That is, loudness∝(amplitude)²

Thus, when amplitude of the wave is halved, the loudness becomes one-fourth.