Question

The slit of width `d` is illuminated by light of wavelength `5000 Å`. If Fresnel distance is `2 m`. What is the slit width ?

Answer 1

Correct Answer - `1 mm`
Here, `lambda = 5000 Å = 5 xx 10^(-7)m, d = ?, Z_(F) = 2m`
As `Z_(F) = (d^(2))/(lambda)`
`:. d^(2) = Z_(F) xx lambda = 2 xx 5 xx 10^(-7) = 10^(-6)`
`d = sqrt(10^(-6) = 10^(-3) m = 1 mm`