Answer to Question #120416 in Optics for Dheeraj

Question

A parallel beam of light of wavelength 5460 Angstrom is incident at an angle of 30 degree on a plane transmission grating with 6000lines/cm. The highest order of observables spectrum is?

Answer 1

$d=1/6000=1.67\cdot 10^{-6}m$

$d(\sin\theta_m+\sin\theta_i )=m\lambda$

For $\theta_m=90°$

$m=\frac{d(\sin\theta_m+\sin\theta_i )}{\lambda}=\frac{1.67\cdot10^{-6}(\sin90°+\sin30° )}{5460\cdot10^{-10}}=1.52\approx2$