A car playing music at a frequency of 250 Hz moves at 20 m/s towards an observer that has frequency. What frequency the observer can hear when
(i) it approaches and
(ii) when it passes by?

(a)

approaching: \(250\times \left( \frac { v+20 }{ v } \right) ;\) leaving: \(\\ 250\times \left( \frac { v-20 }{ v } \right) \)

(b)

approaching: \(\\ 250\times \left( \frac { v }{ v+20 } \right) ;\) leaving: \(250\times \left( \frac { v }{ v-20 } \right) \)

(c)

approaching:\(250\times \left( \frac { v-20 }{ v } \right) ;\) leaving: \(250\times \left( \frac { v+20 }{ v } \right) \)

(d)

approaching: \(250\times \left( \frac { v }{ v-20 } \right) ;\) leaving: \(250\times \left( \frac { v }{ v+20 } \right) \)

Ultrasound waves compared to audible sound waves have.

(a)

Lower frequency and Shorter wavelength

(b)

Lower frequency and longer wavelength

(c)

higher frequency and longer wavelength

(d)

higher frequency and shorter wavelength

The speed of sound in air is 300 m/s. What is the frequency as heard by the human ear?

(a)

0.001 Hz

(b)

1 Hz

(c)

10,000 Hz

(d)

1,00,000 Hz

Distance between two consecutive compressions is

(a)

λ

(b)

λ/2

(c)

λ/4

(d)

2λ

Earthquake produces ______.

(a)

Ultrasound

(b)

Infrasound

(c)

audible sound

(d)

none