Assume a change at the source of sound reduces the wavelength of a sound wave in air by a factor of 3.

(i) What happens to its frequency? It increases by a factor of 9. It increases by a factor of 3. It is unchanged. It decreases by a factor of 3. It changes by an unpredictable factor.
(ii) What happens to its speed?

Explanation:

The speed of a wave is given by :

......(1)

(i) Here, the wavelength of a sound wave in air reduces by a factor of 3. Equation (1) becomes :

Wavelength and frequency are inversely proportional to each other. So, if wavelength of a sound wave in air reduces by a factor of 3, then the frequency will increases by a factor of 3.

(ii) It remains the same.