Images on a Plane Mirror

Light rays and the laws of reflection help determine how and where an image is formed in a plane mirror.

REFLECTION is the bouncing back of light rays from a surface.

Using Light Rays to Locate an Image

We all know that light travels in a straight line.

When your eyes detect reflected light from plane mirrors, your brain projects the light rays back in a straight line.

Laws of Reflection- Review

When a light ray is incident upon reflection surface, the angle of reflection is equal to the angle of incidence.

Both angles are measured relative to the normal.

The incident ray, reflected ray and normal all lie in the SAME plane.

sameangle

Incident ray Reflected rayNormal

Real Images- mirrors can produce images that can be projected on a screen. A real image is ALWAYS inverted and appears in front of the mirror.

Types of Images

Virtual Image- mirrors can also produce images that cannot be projected on a screen. A virtual image is ALWAYS upright and appears behind the mirror.

1. Plane Mirror- a flat mirror that reflects light rays in the same way that they approach the mirror.

2. Concave Mirror- a converging mirror where light rays that strike the mirror surface are reflected so they converge or “come together”, at a point.

Types of Mirrors

3. Convex Mirrors- a diverging mirror where light rays that strike the mirror surface are reflected so that they diverge, or “go apart” and they never come to a point.

SALT is used to describe images formed by mirrors.

1. S- Size: compared to original object is it same size, smaller or bigger?

2. A- Attitude: which way the image is oriented compared to the original object (upright or inverted).

3. L- Location: location of the image (in front or behind the mirror).

4. T- Type: is the image a real image or virtual image?

S.A.L.T

Characteristics of a plane mirror image:

1. Object size= Image Size2. Object distance from mirror= image

distance from mirror3. Attitude (orientation) is ALWAYS

upright4. ALWAYS forms a virtual image5. Image is reversed- left to right

PLANE MIRRORS

The image in a plane mirror appears to be backwards compared to how we view the object directly.

This is why the word on the front of an AMBULANCE is written backwards- so it can be read when seen in a rear-view mirror.

AMBULANCE

Mirrors

1. A ray that strikes perpendicular to the mirror surface, reflects perpendicular to the mirror. The reflected ray is extended beyond the mirror.

2. A ray that strikes the mirror at any angle reflects so the angle of incidence equals the angle of reflection. The reflected ray is extended beyond the mirror.

Steps for drawing Plane Mirror Ray Diagrams:

Perpendicular ray

Incident ray

Reflectedray

Ray Diagram Using 2 Points:

Example: ◦Let’s draw the letter P together on the board

P ?

Using the handout provided, draw these 2 images using the principles of reflection off a PLANE MIRROR.

Use at least 3 points off of the object.

Lets Practice!!

HOMEWORK:

P. 493 #1-4,6, 7 and 11