For diffraction to occur, size of obstacle/aperture must be of the order of wavelength of the waves to be diffracted.
Wavelength of light waves varies from `4 xx 10^(-7) m` to `8 xx 10^(-7)m`. Obstacles/apertures of small size are hardly available. Therefore, diffraction of light waves is not so common. On the contrary, wavelength of sound waves varies from 15 cm to 15 mm. Obstacles/apertures of this size are commonly available. Therefore, diffraction of sound waves is evident in daily life.
