An object is attached to the bottom of a glass plate with indexof refraction 1.5. Three light rays (a, b, c) emanating from theobject are shown; they make angles of 0o (a), 30o (b), and 60o (c)with the normal. An air-filled gap separates the glass plate fromthe front lens of an optical instrument that is used to view theobject. The lens is also made of glass with index of refraction 1.5We are interested in the paths of the rays from the object into thefront lens (how they leave is not our concern).

a)

When is total internal reflection at a glass/air interfacepossible?

Question 17 options:

	For light striking the interface from the glass side.
	For light striking the interface from the air side.
	Never

b)

What happens to ray a as it passes from the glass plate throughthe gap into the front lens?

Question 18 options:

	Ray a is refracted to the right at both interfaces.
	Ray a undergoes total internal reflection.
	Ray a is refracted to the left at the first interface and to theright at the second.
	Ray a goes straight up through both interfaces.

c)

Write an equation for the angle that ray b makes with the normalto the glass-air interface inside the gap. Then calculate the valuein degrees.

d)

For ray b, what is the angle with the normal inside the frontlens?

Question 20 options:

	smaller than 30 degrees
	larger than 30 degrees but smaller than 60 degrees
	60 degrees
	30 degrees

e)

What is going to happen to ray c? Give a brief description ofits path.

f)

Now assume that the gap is filled with oil with a matching indexof refraction, 1.5.

(a) What will happen to the rays now?

(b) What does this imply for the brightness of the object'simage when viewed through the instrument?