Which of the following statements about diffraction is correct?

The correct answer is Option (4) → The colours seen on a CD in white light are due to diffraction.

Diffraction is the spreading of a wave around the edges of an obstacle or an opening. It is seen with every kind of wave.

Option (1) Diffraction is shown by sound waves and light waves but not by matter waves. — Incorrect. Matter waves also show diffraction. Diffraction is seen with sound waves, light waves, water waves and matter waves.

Option (2) Diffraction of light is rarely seen in daily life because most obstacles are smaller than its wavelength. — Incorrect. The size comparison is the other way round. The wavelength of light is much smaller than most obstacles. That is why we do not see diffraction of light in daily life.

Option (3) Light spreads into the shadow behind a narrow slit because of refraction at its edges. — Incorrect. Refraction is the bending of light when it goes from one medium into another. Light turning around the edges of a slit into the shadow region is diffraction, and it is explained by wave ideas.

Option (4) The colours seen on a CD in white light are due to diffraction. — Correct. The colours on a CD come from diffraction of white light. The positions of the bright bands depend on wavelength, so each colour appears at a different place.

NCERT (2026-27):
Diffraction – “… Indeed the colours that you see when a CD is viewed is due to diffraction effects.”