Mirrors & LensesMirrors & LensesHow Light Moves

When light strikes an object, 3 things can happen.

ReviewReview

The light can be:

TransmittedReflected Absorbed

Incident Ray Normal Reflected Ray

Angle of incidence

Plane Mirror

Light reflects off a plane (flat) mirror in a certain way.

Angle of reflection

Reflection Off A Plane MirrorReflection Off A Plane Mirror

The Law of ReflectionThe Law of ReflectionThe Law of Reflection states that for a plane mirror:

Incident Ray Normal Reflected Ray

Angle of incidence

Plane Mirror

Angle of incidence

Angle of Incidence = Angle of Reflection

Light rays reflect off a plane mirror in a regular way.

Angle of Incidence = Angle of ReflectionThis makes the light rays seem to come from behind the mirror at an equal distance..

Images In A Plane MirrorImages In A Plane Mirror

This forms an image that is upright and the same size.

It is a virtual image, since the light is not actually

coming from the image.

Forming A Virtual ImageForming A Virtual Image

Virtual Image

Upright

Same Size

Reversed

Concave mirrors have surfaces that curve inward.

A concave mirror reflects light rays so that they converge (meet) at a certain point.

Concave MirrorsConcave Mirrors

We call this point the focal point of the mirror.

Concave mirrors form images in 2 different ways.

The type of image depends on the distancethe object is placed from the focal point.

Concave MirrorsConcave Mirrors

Focal Point

1. Object is placed behind the focal point.

Real Image

Upside down

Smaller

2. Object is placed in front of the focal point.

Virtual Image

Upright

Larger

Convex mirrors have surfaces that curves outward.

A convex mirror reflects light rays so that they diverge (spread out).

Convex MirrorsConvex Mirrors

The light rays do NOTmeet at a focal point in front of the mirror.

Convex mirrors ALWAYS form images the same way.

A convex mirror forms a virtual imagethat is smaller than the true object.

Convex MirrorsConvex Mirrors

Focal Point

Refraction is when light rays are bent.

When light rays pass from one material to another, the light rays refract (bend).

RefractionRefraction

The rays change directionwhere the 2 materials meet.

The light bends because it changes speed in different

materials (mediums).

RefractionRefraction

Light travels fast

Light travels slow

Medium 1 - Air

Medium 1 - Water

Index of RefractionIndex of RefractionSome mediums refract light rays more than others.

This is described by the index of refraction.

Index of RefractionIndex of RefractionSome mediums refract light rays more than others.

This is described by the index of refraction.

Index of RefractionIndex of RefractionSome mediums refract light rays more than others.

This is described by the index of refraction.

Index of RefractionIndex of RefractionIndexes of Refraction for Common Materials

Vacuum 1.00

Air 1.01

Water 1.33

Glycerine 1.47

Glass 1.52

Diamond 2.42

A lens is a curved device that refracts light precisely.

Lenses are useful because they can refract light rays in a predictable way.

LensesLenses

There are 2 types of lenses:

Concave Convex

A concave lens is thinner in the middle.

A concave lens bends parallel light rays to make them diverge.

Concave LensConcave Lens

Produce a virtual image

only

A convex lens is thicker in the middle.

A convex lens bends parallel light rays so that they meet at a focal point.

Convex LensConvex Lens

Produce a real or a

virtual image

Lenses have many uses.

LensesLenses

Any Questions?Any Questions?