What is the correct way to separate light into its component colors?

[physgrl]

Homework Statement

1. Light can be separated into its component colors by:

a. diffraction gratings

b. thin film interference

c. focusing a broad beam of light into a point

d. bends light as it passes the edge of an object

*e. both a and b

The Attempt at a Solution

I thought the answer was c because it seems like what happens in a prism, but apparently (answer key) its e. Can someone explain why? Thanks!

 

[tal444]

C, focusing a broad beam of light into a point is simply intensifying the light, kind of like using a magnifying glass to burn something. A prism slows down the wavelengths just enough so that the different wavelengths separate.

 

[physgrl]

ok but why do diffraction gratings separate the colors?

 

[tal444]

http://en.wikipedia.org/wiki/Diffraction_grating

From the article above: "In optics, a diffraction grating is an optical component with a periodic structure, which splits and diffracts light into several beams traveling in different directions. The directions of these beams depend on the spacing of the grating and the wavelength of the light so that the grating acts as the dispersive element."