Physical Science / Unit 9: Waves, Sound and Light
9.6 Refraction and Lenses
Notes
Refraction is the bending of a wave when it enters a different medium and changes speed.
- Light slows down in water or glass, so it bends toward the normal when going from air into them.
- Refraction makes a straw look bent in water and causes a prism to split white light into colors (dispersion), since different colors bend by different amounts.
- A convex (converging) lens is thicker in the middle and focuses light, as in magnifiers and the eye. A concave (diverging) lens is thinner in the middle and spreads light.
- A rainbow forms from refraction and reflection in water droplets.
Practice
Refraction occurs because light:
Speed change at the boundary causes bending.
Which lens can focus parallel light rays to a point?
A convex lens converges light.
A prism separates white light into colors because:
White light contains all colors, which bend differently.
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