10.1 RecapLight and how we

perceive it

Optical illusions are pictures that can be perceived differently than the reality of the picture.

There are several types of illusions but we will examine a few and demonstrate how each works and what is happening in your head as you view the images.

Take your time and don’t yell out your responses until others have had time to figure them out, please!!!!!

Now for the fun stuff....

Optical Illusion #1

What do you see?

§ Optical Illusion #2

What do you see?

§Look at the next slide for 3 seconds only and tell me what you see.

§ Optical Illusion #3

Do you see only coffee beans?

§ Optical Illusion #4

What do you see?

§ Optical Illusion #5

What do you see?

What do you see?

10.2Properties of Light

and Reflection10.2 – Learning Goals

§ I will be able to explain how light travels in straight lines

§ I will be able to explain how plane mirrors work§ I will be able to locate/describe how an image is

formed in a plane mirror

§ Describe what you see in this image?

Reflection

Reflection§ the change in direction of a light ray when it

bounces off a surface

Rays of Light§ light travels in a straight line (as long as it’s moving

through the same medium)§ medium – the substance through which light travels

§ ray diagrams can be used to make predictions about appearance of objects

Reflection of Light Video

Reflection of Ray of Light by a Plane Mirror

Definitions You Need to Know

§ incident ray – a ray of light that travels from a light source towards a surface

§ angle of incidence – angle between the incident ray and the normal in a ray diagram

§ normal - a line that is perpendicular to a surface where a ray of light meets the surface

§ reflected ray – a ray that begins at the point where the incident ray and the normal meet

§ angle of reflection – the angle between the reflected ray and the normal in a ray diagram

§ plane mirror – a mirror with a flat reflective surface

Laws of Reflection

1. The incident ray, the reflected ray, and the normal always lie on the same plane.

2. The angle of reflection is equal to the angle of incidence.

r = i

Virtual Image

§ brain assumes that a light ray travels in a straight line

§ note the lateral inversionall images in plane mirrors are reversed

§ an image formed by rays that appear to be coming from a certain position, but are not actually coming from this position

§ image does not form a visible projection on a screen

Virtual Image

Abraham Lincoln

Abraham Lincoln

Left side face

Abraham Lincoln

“Left side” face “Right side” face

Four Characteristics of an Image

1. Location § closer than, farther than, or the same distance as

the object to the mirror2. Orientation

§ upright or inverted3. Size

§ same size, larger than, or smaller than the object4. Type

§ real or virtual image

L.O.S.T

“Orientation”

Characteristics of an Image in a Plane Mirror

1. Location § the same distance as the object to the mirror

2. Orientation § upright

3. Size § same size

4. Type § virtual image

§ You can predict these characteristics by drawing a ray diagram

TAKE OUT…

• Your ruler…..

• Your Protractor…

• Your pencil…

• Look at: 10.2 – Locating an Image using a Ray Diagram

Locating an Image in a Plane Mirror Using a Ray Diagram

Locating an Image in a Plane Mirror Using a Ray Diagram

Locating an Image in a Plane Mirror Using a Ray Diagram

Locating an Image in a Plane Mirror Using a Ray Diagram

Locating an Image in a Plane Mirror Using a Ray Diagram

RAY DIAGRAM SUCCESS CRITERIA

What makes this picture perfect?

• ?

Now can you explain this image…

LAWS OF REFLECTION

https://www.youtube.com/watch?v=vt-SG7Pn8UU

Homework§ Read p. 411-416 in the textbook.§ Complete Q. 1-4, 6, 7 p. 418.§ Complete “The Law of Reflection” in class

assignment

§ Video Game: http://www.shockwave.com/gamelanding/energy-spectrum.jsp