Question

When a light ray travels from water to air, the wave_____________________.

	A.	slows down and bends away from the normal
	B.	speeds up and bends toward the normal.
	C.	speeds up and bends away from the normal
	D.	slows down and bends toward the normal

Answer 1

To find the answer we must look at two laws.

First law would be snail's law that states mathematically

Where let's say n₁ is the refractive index of air and n₂ is of water. And are the angle that the refracted and incident light ray makes with the normal respectively.

Now we can rearrange this formula to see that

Which implies that the angle that refracted ray makes with normal is greater than the incident ray makes with the normal. So the light ray bends away from the normal.

Now the speed of monochromatic Electromagnetic waves in any medium is given as

Where c is the speed of light in vacuum which is a universal constant.

This implies

v×n= constant

So v₁×n₁=v₂×n₂

_or

Again n₂>n₁

so

which implies that speed of the wave in air is greater than that of in water.

now with this we can conclude that:

C.The wave speeds up and bends away from the normal.