Diffraction Gratings

Light is shone on to a diffraction grating. If the distance between the slits is d, then the path difference between successive diffracted beams isso Sincethere is a maximum order for n.

Example: L Light of wavelengthis incident on a diffraction grating which has 600000 lines per metre. Find all the angles corresponding to the maxima.

If there are 600000 lines per m,

Ifdegrees.

Ifdegrees.

Ifdegrees

Ifdegrees.

Ifand this has no solution, so the maximum value for the order is 4. Note that there is one fringe on either side and a bright fringe in the middle so if a diffraction pattern hasorders there arefringes.