# Problem: A commercial diffraction grating has 400 lines per mm. When a student shines a 490 nm laser through this grating, how many bright spots could be seen on a screen behind the grating.

###### FREE Expert Solution

Diffraction:

$\overline{){\mathbf{d}}{\mathbf{s}}{\mathbf{i}}{\mathbf{n}}{\mathbf{\theta }}{\mathbf{=}}{\mathbf{m}}{\mathbf{\lambda }}}$

m is the order while d is the spacing of the grating.

The number of spots for a given order:

θ = 90° for the total number of bright spots.

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###### Problem Details

A commercial diffraction grating has 400 lines per mm. When a student shines a 490 nm laser through this grating, how many bright spots could be seen on a screen behind the grating.