UPSEE 2018 Solved Paper

Diffraction of light at a single slit, the pattern obtained consists of a central bright band having alternate dark and weak bands of decreasing intensity on both sides.
For nth minima (secondary),
sin‌θn=

nλ

a

For nth maxima (secondary),
sin‌θn=(2n+1)

λ

2a

Thus, point 5 corresponds to path difference of extreme rays equal to 2λ.