Question

I think this is a single slit diffraction, but I need help

Light from an argon laser produces light at lambda = 515 nm. This light is used to form a diffraction pattern through a diffraction grating with slit spacing of 2 mu m. The interference pattern is observed on a screen 0.7 m behind the slits. Draw a picture to show both a & b: a. What's the maximum number of bright fringes that could be observed. b. What is the distance between the second and third order diffraction fringes?

Answer 1

a)

d = slit spacing = 2 um = 2 x 10^-6 m

$\lambda$ = wavelength = 515 nm = 515 x 10^-9 m

n = number of brightt fringes

$\theta$ = 90

using the formula

d Sin $\theta$ = n $\lambda$

for maximum number of fringes

$\theta$ = 90

n = d/ $\lambda$

n = ( 2 x 10^-6)/(515 x 10^-9)

n = 3.88 $\approx$ 4

b)

w = spacing = D $\lambda$ /d = (0.7) (515 x 10^-9)/( 2 x 10^-6) = 0.18025 m