Choose the wrong statement

The correct answer is Option (4) → Diffraction pattern is due to the superposition of two coherent rays from two sources

Interference in Young's experiment comes from two waves from two coherent slits; diffraction at a single slit comes from the superposition of a continuous family of wavelets from different parts of the same wavefront in that one slit.

Option (1) Interference pattern has a number of equally spaced bright and dark fringes — True statement. The fringe width \( \beta = \lambda D/d \) is the same for all fringes.

Option (2) The diffraction pattern has a central maximum which is twice as wide as the other maxima — True statement. For a single slit the central maximum spans \( 2\lambda/a \) in angle, while each secondary maximum spans \( \lambda/a \).

Option (3) Interference pattern is due to the superposition of two waves originating from the two narrow slits — True statement. It is formed by the two waves coming from the two slits.

Option (4) Diffraction pattern is due to the superposition of two coherent rays from two sources — Wrong statement. The diffraction pattern is produced by wavelets from different points of a single slit, not by two rays from two separate sources.

NCERT (2026-27):
Interference of Light Waves and Young’s Experiment – “… Equations (10.13) and (10.14) show that dark and bright fringes are equally spaced.”

The Single Slit – “… We are treating different parts of the wavefront at the slit as secondary sources.”

The Single Slit – “… The best we can do is, roughly speaking, is to say that when there are only a few sources, say two interfering sources, then the result is usually called interference, but if there is a large number of them, it seems that the word diffraction is more often used.”