What will be the change in the wavelength of a sound wave in air if its frequency is doubled?
Answer
Velocity of sound = Frequency $\times $ wavelength Speed of sound in air is constant.
Hence, frequency $\times $ wavelength = constant If frequency is doubled, wavelength is reduced to half.
Which of the following sound frequencies cannot be heard by a human ear?
$(i) 10\ Hz$
$ (ii) 100\ Hz$
$ (iii) 10,000\ Hz $
$(iv) 15\ Hz$
$ (v) 40,000\ Hz.$
Answer
The sound frequencies that cannot be heard by a human ear are $10\ Hz, 15\ Hz$ and $40,000\ Hz$.
State one observation from everyday life which shows that sound travels much more slow than light.
Answer
It is common observation that in the rainy season, the flash of lightning is seen first and the sound of thunder is heard a little later. That’s because, speed of light is very high as compared to speed of sound in air.