J.M. Gabrielse

Ray Diagrams

J.M. Gabrielse

A ray of light is an extremely narrow beam of light.

J.M. Gabrielse

All visible objects emit or reflect light rays in all directions.

J.M. Gabrielse

Our eyes detect light rays.

J.M. Gabrielse

We see images when light rays

converge in our eyes.

converge: come together

J.M. Gabrielse

Mirrors

object

image

It is possible to see images in mirrors.

This is a plane mirror, such as you would see in a bathroom.

J.M. Gabrielse

Mirrors reflect light rays.

J.M. Gabrielse

Reflection(bouncing light)

Reflection is when light changes direction by bouncing off a surface.

When light is reflected off a mirror, it hits the mirror at the same angle (the incidence angle, i) as it reflects off the mirror (the reflection angle, r).

The normal is an imaginary line which lies at right angles to the mirror where the ray hits it.

r i

Mirror

normal

incident ray

reflected ray

J.M. Gabrielse

Interactive mirror activity

Students can manipulate mirrors to reflect light in different directions:

http://www.bbc.co.uk/schools/ks2bitesize/science/activities/see_things.shtml

Now try this one:

http://www.bbc.co.uk/schools/scienceclips/ages/10_11/see_things_fs.shtml

J.M. Gabrielse

Virtual Images

• When an object's image lies behind the mirror, the image is called a virtual image.

J.M. Gabrielse

Plane Mirrors(flat mirrors)

How do we see images in mirrors?

J.M. Gabrielse

Plane Mirrors(flat mirrors)

object image

Light reflected off the mirror converges to form an image in the eye.

How do we see images in mirrors?

J.M. Gabrielse

Plane Mirrors(flat mirrors)

object image

Light reflected off the mirror converges to form an image in the eye.

The eye perceives light rays as if they came through the mirror.

Imaginary light rays extended behind mirrors are called sight lines.

How do we see images in mirrors?

J.M. Gabrielse

Plane Mirrors(flat mirrors)

object image

Light reflected off the mirror converges to form an image in the eye.

The eye perceives light rays as if they came through the mirror.

Imaginary light rays extended behind mirrors are called sight lines.

The image is virtual since it is formed by imaginary sight lines, not real light rays.

How do we see images in mirrors?

J.M. Gabrielse

Characteristics of Images in Plane Mirrors

•S(size) Image size is equal to object size.

•P(position) Image distance is equal to object distance.

•O(orientation) The image is upright. (Its orientation is the same as that of the object.)

•T(type) The image is virtual (object's image lies behind the mirror).

• Another interesting feature is that all images in a mirror are reversed, right to left and left to right, compared to the objects being reflected.