Question

A parallel beam of light of 500nm falls on a narrow slit and the resulting diffraction pattern is observed on a screen 1m away. It is observed that the first minimum is at a distance of 2.5mm from the centre of the screen. Calculate the width of the slit

Answer 1

Hint: From condition of diffraction,
sinθ =nλ (for minima)

= (n + 1/2)λ for maxima
Provided n =1, 2, 3...and n = 0 for central maxima
From condition of minima,
asinθ = λ      (n =1)
Since the value of λ is of nm, so