Question

A diffraction grating is illuminated with yellow light at normal incidence. The pattern seen on a screen behind the grating consists of three yellow spots, one at zero degrees (straight through) and one each at ±45°. You now add red light of equal intensity, coming in the same direction as the yellow light. The new pattern consists of1. red spots at 0 and +/- 45

2. yellow spots at 0 and +/- 45
3. Orange spots at 0 and +/- 45
4. an orange spot at 0, yellow spots at +/- 45, and red spots slightly further out
5. an orange spot at 0, yellow spots at +/- 45, and red spots slightly closer in

Answer 1

4. an orange spot at 0, yellow spots at +/- 45, and red spots slightly further out

Step-by-step explanation:

At central place ( zero degree ) central maxima of both the color will be formed resulting into formation of orange spot there. At +/- 45 degree , yellow spot will be formed as before . For red light , wave length is larger so fringe width will be greater . Hence fringe will be formed farther away from the region of central maxima. It means red spot will be observed farther away or out.