Question

Number of line per centimeter of a plan diffraction grating is 6000.when a monochromatic light is incident on it the angle of diffraction for the second order spectral line become 450.find the wavelength of the light.

Answer 1

Answer

equation for diffraction grating

$d\sin\theta=n\lambda$

No. Of spectral line per centimeter

1/d=6000

In first case

$\lambda=\sin\theta/6000$

Now in second case

Wavelenth

$\lambda'=\frac{\sin\theta}{6000\times2\times sin\theta\times450}=0.9A^°$