Types of Mirrors

Concave Mirrors

Mirrors that curve inwards are known as Concave Mirrors

E.g. if you look into the front of a spoon, you are looking at a concave mirror

Shape:

Like an hourglass

E.g. The Spoon

The inside of the spoon (where the liquid and food is placed)

Converging Mirrors:

Concave mirrors cause light rays to converge or focus on one point in front of the mirror

Narrowed in

Therefore, they are also known as converging mirrors

Plane

Shape:

Rectangle, exactly the way it is

Convex

In a convex mirror, the mirror curves outwards

This is what you would see if you looked into the back of a spoon

Shape:

Always curves outwards

A rounded figure, a ball figure/shape

E.g. The Spoon

The outside of the spoon (where there is no liquid or food placed)

Diverging Mirrors (Convex Mirror)

Convex mirrors cause light rays to diverge or to spread out

Therefore, they are known as diverging mirrors

They spread out and widen the reflection

Parts of Ray Diagram for Curved Mirrors

Vertex: the center of the curved mirror

Center of curvature (C): is the radius of the imaginary sphere that the mirror is cut out from

Focus (F): where parallel light rays converge; approximately halfway between the centre of curvature and the vertex

Principal Axis: the line that is perpendicular to the vertex of the curved mirror (similar to the normal in flat mirrors)

Ray Diagram Conventions

Ray 1#: Any ray that is parallel to the PA is reflected through F

From the top of the object, goes straight across bounces off the top of the curve first and then goes through F → It’s fine

Ray 2#: Any ray that passes through F is reflected parallel to PA

Go Down and go through F first and then bounce off the curve then reflect off straight across→ It’s fine

Ray 3#: Any ray that passes through C is reflected along the same path

Downs and goes through/hits C → it’s fine

Ray 4#: Any ray that hits the vertex is reflected at the same angle

Hits the vertex and bounces off the curve, but can bounce off anywhere → it’s fine

Note: THEY ALL MEET AT ONE POINT; LIKE THE POINT OF INTERSECTION

The Rays

Note: you only need any 2 of the 4 possible rays that you can draw to locate an image!

→ Use rays 1 and 2 when the object is before F (left of F)

If the object is before the F point, then you use line 1 and 2 to find the location of the object

→ Use rays 1 and 3 when the object is on or after F (right of F)

If the object is after the F point, then you use line 1 and 3 to find the location of the object

The Acronym SALT - Ray Conventions

S = Size

How big is the image, relative to the object?

A = Attitude (upright or inverted)

Is the image upright or inverted

L = Location

Where on the principal axis is the image located?

T = Type

Is it a “real” or “virtual” image?