Laws of Reflection and Refraction Lecture 2

Question 1

Light striking an interface between two media, and entering the new medium changes what?

Answer 1

Velocity, and a change in direction in most cases.

Question 2

During transparency, light part of the light is ________, most ________ and some of the material is ___________.

Answer 2

Reflected; refracted; absorbed.

Question 3

There are two types of reflection. What are they? Which so we care about more?

Answer 3

Specular and diffuse. Consider specular reflection in geometrical optics.

Question 4

The angle of incidence is equal to the angle of reflection is known as what law?

Answer 4

Law of Reflection.

Question 5

Light which is reflected leaves the surface traveling in what direction?

Answer 5

Opposite.

Question 6

What is Fresnel’s Law of Reflection?

Answer 6

R=(n’-n/n’+n)^2 x 100
n=refractive index of objects space (left of interface)
n’=refractive index of image space (right of interface).

Question 7

What does Fresnel’s Law of Reflection describe?

Answer 7

Amount of light reflected from otherwise transparent and refractive interface (not for mirrors) in percentage.

Question 8

What is the index of refraction of a medium?

Answer 8

n=c/v
c=speed of light in a vacuum (3 X 10^8 m/s)
v=speed of light of a different medium.

Question 9

The more denser the medium, the _____ the speed of light for that medium, the ______ the refractive index for that medium.

Answer 9

Lower; higher.

Question 10

For any optic problem without a specified refractive index, what value do you use?

Answer 10

1.50.

Question 11

In reality though, the refractive index (n) depends on what two things?

Answer 11

Frequency and wavelength.

Question 12

Since f is constant, the refractive index depends upon the wavelength of light used. What wavelength i sued as a reference wavelength?

Answer 12

589.30 nm.

Question 13

True or False: Refractive index is wavelength independent.

Answer 13

False. Dependent.

Question 14

The Law of Refraction is also known as what?

Answer 14

Snellen’s Law.

Question 15

What is the Law of Refraction?

Answer 15

Says refraction occurs when light passes from one medium into another medium.

Question 16

What is the formula of Snellen’s Law?

Answer 16

The index of the medium before refraction times the sine of incident angle is equal to the index of the medium after refraction times the sine of refracted angle.
n X sin 0 =n’ X sin 0’.

Question 17

When going from a less dense into a more dense material, angle of incidence is _________ then the angle of refraction.

Answer 17

Greater.

Question 18

When going from a more dense into a less dense material, angle of incidence is _________ then the angle of refraction.

Answer 18

Less.

Question 19

The largest possible angle for 0 or 0’ is what?

Answer 19

90 degrees.

Question 20

Going from a more dense into a less dense material, when the angle of incidence exceeds a critical angle (say 70 degrees), all the light is reflected internally. What is this called what?

Answer 20

Total Internal Reflection.

When angle of refraction is larger than the angle of incidence

Question 21

True or False: Total internal reflection occurs when light is in a more dense medium and wants to go into a less dense medium,.

Answer 21

True.

Question 22

What practical application in Optometry is there that some what proves the total internal reflection theory?

Answer 22

Sclerotic scatter.

Question 23

Why do we see mirages?

Answer 23

Happens only on hot days because cements becomes a lower refractive index than the sky so total internal reflection occurs due to high medium to low medium light refraction.