In double slit experiment, the wavelength λ of the light source 400 nm, the slit separation d is 20 μ m and the individual slit width' a is 4 μ m. Consider the interference of the light from the two slits and also the diffraction of light through each slit. Find number bright interference fringes are within the central peak of diffraction envelope.

Question

In double slit experiment, the wavelength λ of the light source 400 nm, the slit separation d is 20 μ m and the individual slit width' a is 4 μ m. Consider the interference of the light from the two slits and also the diffraction of light through each slit. Find number bright interference fringes are within the central peak of diffraction envelope. (A)  (B)  (C)  (D)

Tardigrade Admin · Accepted Answer

We know that d sin θ=n λ for interference and a sin θ=λ for diffraction ∴ (d/a)=n=(20/4)=5. So interference maxima's is 9

We know that dsinθ=nλ for interference and asinθ=λ for diffraction ∴ad​=n=420​=5. So interference maxima's is 9

We know that
$d sin θ = nλ$ for interference
and $a sin θ = λ$ for diffraction
$∴ \frac{d}{a} = n = \frac{20}{4} = 5$ .
So interference maxima's is $9$