Subject: Applied Physics 2

Topic: Interference And Diffraction

Difficulty: Medium

Width W = 3 cm, N = 7000 lines/cm, λ = 5000 A°

grating element $(a+b) = \frac{1}{N} = \frac{1}{7000}$

RP is maximum when n is maximum

N is maximum when sin θ =1

(a+b) sin θ = n λ

$n_{max} = \frac{1}{Nλ} = \frac{1}{ 7000 \times 5000 \times 10^{-8}} = 2.8$

n cannot be 3 as sin θ exceeds one

n$_{max}$ = 2

RP = n N

RP = 2x7000 x 3 as grating is 3 cm wide

RP = 42000