Assertion : Diffraction is common in sound but not common in light waves. Reason : Wavelength of light is more than the wavelength of sound.

Step-by-step solution

For diffraction of a wave, size of an obstacle or aperture should be comparable to the size of wavelength of the wave. As wavelength of light is of the order of 10⁻⁶ ~m and obstacle / aperture of this size are rare, therefore, diffraction is not common in light waves. On the contrary, wavelength of sound is of the order of 1 ~m and obstacle / aperture of this size are readily available, therefore, diffraction is common in sound.