Question

The parallel beam of light from a monochromatic source (λ = 0.6μm) falls onto

the slit of the width a = 0.1 mm. Determine the breadth (width) l of the central maximum

in the diffraction pattern that is projected onto the screen by the lens situated directly behind

the slit, i.e. the lens is between the slit and the screen. The screen is at the distance L = 1m

from the lens.

Answer 1

The width of central maximum is

$$l=\dfrac{2L\lambda}a=0.012\text{ m}.$$