Chapter 18.2- Reflection

Question 1

What is specular reflection?

Answer 1

The reflection from a smooth, shiny surface such as a mirror or a piece of polished metal

Question 2

From a 3D perspective, where is the plane that both incident and reflected rays are in?

Answer 2

The incident and reflected rays are in the plane of the page. This plane is located normal to the surface.

Question 3

Where does a reflected surface extend past?

Answer 3

A reflective surface extends into and out of its page.

Question 4

What is ONE thing we NEEED to remember about single light rays? What do they represent?

Answer 4

Single light rays represent the entire bundle of parallel rays(“This is oversimplified, but it keeps the figure and the analysis clear.” -Tanja’s words).

Question 5

What is the angle of incidence?

Answer 5

The angle theta(i) between the incident ray and a line perpendicular to the surface->the normal to the surface

Question 6

What is the angle of reflection?

Answer 6

The angle theta(r) is the angle between the reflected ray and the normal to the surface

Question 7

What are the two things the law of reflection states?

Answer 7

1. The incident ray and the reflected ray are both in the same plane, which is perpendicular to the surface
2. The angle of reflection equals the angle of incidence

Question 8

What is a diffuse reflector?

Answer 8

Paper or cloth

Question 9

What is the surface of a diffuse reflector like on a microscopic scale?

Answer 9

It’s rough

Question 10

How does the rough surface of a diffuse reflector affect its reflected ways? Does the law of reflection still hold?

Answer 10

The irregularities of the rough surface cause the reflected rays to leave in all directions.

Yes, the law still holds

Question 11

What is a plane mirror?

Answer 11

A flat mirror

Question 12

How do rays from point P reflect from a plane mirror?

Answer 12

According to the law of reflection.

As rays from P reflect from the mirror, each ray obeys the law of reflection

Question 13

In a diagram concerning reflection from a plane mirror, what do dashes lines mean?

Answer 13

The dashed lines indicate that the rays appear to have come from point P’. And actually ALLLL reflected rays come from point P’

Question 14

What is the virtual image of P?

Answer 14

It’s point P’. It is where the reflected rays diverge

Question 15

Why is the virtual image of P (point P’) virtual??

Answer 15

The image is virtual because no rays actually leave Point P’, but the light waves act exactly as if they were

Question 16

How does the eye react to this plane mirror?

Answer 16

The eye captures and focuses diverging bundles of rays from each point of the image (of an extended object) in order to see the full image in the mirror

Question 17

What are two important facts that we need to remember about plane mirrors?

Answer 17

1. Rays from each point on the object spread out in all directions and strike EVERY POINT on the mirror. Only a few of these rays enter your eye, but the other rays are very real and might be seen by other observers
2. Rays from points P and Q enter your eye reflecting from DIFFERENT areas of the mirror. This is why you can’t always see the full image in a small mirror