Question

We use both AC and DC electricity. Carefully (in terms of physics!) describe differences between these two types of electricity, including advantages and/or limitations.

Which statements are true about rainbows? Rainbows happen because:

1. Water is dispersive.
2. Interference allows us to see constructive interference for green at a different position than constructive interference for purple.
3. In water, the index of refraction of red is different than the index of refraction of green.
4. Inside each droplet, the light hitting the back of the drop has an incident angle smaller than the critical angle for the water-to-air boundary.

		Only 1 and 2 are true.
		Only 3 and 4 are true.
		All are true.
		Only 1 and 3 are true.
		Only 1, 3, and 4 are true.

Answer 1