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In a plane transmission grating, the angle of diffraction for the second order maxima for wavelength $5 × 10^{-5}$ cm is $30^o$.

Mumbai university > FE > SEM 2 > Applied Physics II

Marks: 5M

Year: May 2014

Given:

$θ = 30^o$

$n = 2$

$λ = 5 × 10^{-5} cm$

To find:

No. of lines/cm = $\frac{1}{d}$

Solution:

We know that for principal maxima

$d sinθ = nλ$

$\frac{1}{d} = \frac{sin θ}{nλ}$

$\frac{1}{d} = \frac{sin 30}{2 × 5 × 10^{-5}}$

$\frac{1}{d} = 5000$

No. of lines per cm is 5000