Chapter 18

Question 1

what is a wave front?

Answer 1

a surface passing through points of a wave that have the same phase and amplitude

Question 2

what is ray approximation?

Answer 2

is used to represent beams of light

Question 3

what is an incident ray?

Answer 3

travels in a medium, some light is reflected back

Question 4

what is a refracted ray?

Answer 4

the refracted ray enters the second medium and is bent at the boundary

Question 5

the incident ray is equal to the…?

Answer 5

the incident ray is always equal to the reflected ray

Question 6

what is specular reflection?

Answer 6

is reflection from a smooth (highly polished) surface

Question 7

what is diffuse reflection?

Answer 7

is reflection from a rough surface, the reflected rays travel in a variety of directions

Question 8

what is snell’s law?

Answer 8

The angle of refraction depends on the indices of the two media
n1sinθ1 = n2sinθ2

Question 9

LHC means?

Answer 9

Low to High index means the refracted ray bends closer to the normal line

Question 10

HLA means?

Answer 10

High to Low index means the refracted ray bends away from the normal line

Question 11

Violet light does what?

Answer 11

violet light bends more towards the normal line than red

Question 12

what total internal reflection?

Answer 12

can occur when light attempts to move from a medium with a higher index of refraction to one with a lower index of refraction (HLA)
n1sinθc = n2sin(90)

Question 13

how to see objects with a flat mirror?

Answer 13

the reflected rays follow the law of reflection

Question 14

what are the properties of flat mirrors?

Answer 14

s = s'
h = h'
m = 1 ALWAYS
the image is always virtual
the image has the same orientation as the object

Question 15

what is a concave mirror (positive f) (rays are reflected not refracted)?

Answer 15

it curves inward like a cave
Principal Rays for a concave mirror:
1. ray in parallel to axis, out through f
2. ray in through f, out parallel to axis
3. ray in through c, out along itself
4. in to V, then law of reflection θi = θr

Question 16

what is a convex mirror (negative f) (rays are reflected not refracted)?

Answer 16

it curves outward opposite of a cave
Principal Rays for a convex Mirror:
1. ray in parallel to axis, out as if from f
2. ray in towards f, out parallel to axis
3. ray in towards C, out along itself
4. ray in to V, then law of reflection θi = θr

Question 17

For a concave mirror what do these stand for?

Answer 17

BUV = Bigger, Upright, Virtual (when image is between the mirror and the focal point) 
SIV = Smaller, Inverted, and Real (when image is beyond the focal point)

Question 18

For a convex mirror what is the ONLY possible outcome for images?

Answer 18

SUV = smaller, upright, virtual

Question 19

For mirrors, what does real and virtual mean?

Answer 19

Real : image formed in front of mirror
Virtual : Image formed behind the mirror
THIS IS OPPOSITE FOR LENSES

Question 20

what are converging lenses?

Answer 20

Positive focal lengths, thickest in the middle

Question 21

what are diverging lenses?

Answer 21

Negative focal lengths, thickest at the edges

Question 22

what is the lens-maker’s equation?

Answer 22

1/f = (n-1)(1/R1 - 1/R2)

Question 23

What are the Principal Rays for Thin lenses (rays refracted so they pass through the lens, they are not reflected)?

Answer 23

1. Ray in parallel to axis, out through f
2. Ray in through C, out through C
3. Ray in through f, out parallel

Question 24

What do you do for combinations of two lenses?

Answer 24

• Pretend as if the second lens was not there and find your image for the first lens
• then the image of the first lens becomes your object for your second lens
• the total magnification M is the product of the two separate lenses:

M =m1m2