28Diffraction Diffraction GratingsHard1 mark
A beam of white light is incident normally on a diffraction grating.
Three bands of bright fringes are formed on a screen, labelled 1, 2 and 3 as shown.
What are the colours of the fringes seen on the screen?
| 1 | 2 | 3 | |
|---|---|---|---|
| A | continuous spectrum, red → violet | white | continuous spectrum, violet → red |
| B | continuous spectrum, violet → red | white | continuous spectrum, red → violet |
| C | continuous spectrum, red → violet | continuous spectrum, red – violet – red | continuous spectrum, violet → red |
| D | continuous spectrum, violet → red | continuous spectrum, violet – red – violet | continuous spectrum, red → violet |