Question

Diffraction of sound is very easy to observe in day-to-day life. This is not so much with light. This is so because
(A) ${\lambda _S} > {\lambda _L}$
(B) ${\lambda _S} < {\lambda _L}$
(C) Light waves are transverse and sound waves are longitudinal
(D) ${\lambda _S} = {\lambda _L}$

Answer 1

Diffraction is a phenomenon where a wave bends when it passes through an obstacle or an aperture. This causes the wave to spread out to other areas like places where the geometrical shadow of that obstacle must form.

Complete Answer:
When a wave passes through an obstacle or an aperture, it diffracts on the edges of that obstacle, this phenomenon is called Diffraction of a wave. Diffraction causes the wave to spread out and allows it to travel along different routes.
We can hear a sound even if there is a wall (or numerous walls) between the listener and the source of the sound. This is because sound diffracts at the edges of a door or any other aperture, and reaches us.
But a beam of light cannot reach a viewer if it is obstructed by an object kept between the viewer and the source of light. This is because the beam of light does not diffract when a large object is kept in front of it.
This difference in the amount of diffraction by light and sound even though they are both waves, is because of the difference in their wavelengths.
For diffraction to properly occur, the size of the obstacle or aperture must be in the same order of magnitude as the wavelength of the wave.
For sound waves, the wavelength varies from meters to centimetres, which is the size of obstacles we encounter in our day to day lives.
Whereas for visible light waves the wavelength exists on a nanometer scale, it is hard to see or have objects that contain such a small aperture, this is why diffraction in light is not easy to observe in day-to-day life.
Therefore, the reason why this happens is because, ${\lambda _S} > {\lambda _L}$. Therefore, option (A) is correct.

Note:
Light is an electromagnetic wave, for electromagnetic waves other than light, the wavelength might be in the same order of magnitude as the objects around us, thus these waves diffract around such objects, this has many applications as well like cell phones use microwaves for communication or FM radios use radio waves for broadcasting services.