1. Mirrors & Lenses
How Light Moves

2. Review
When light strikes an object, 3 things can happen.
The light can be:
Reflected Transmitted Absorbed

3. Reflection Off A Plane Mirror
Light reflects off a plane (flat) mirror in a certain way.
Incident Ray Normal Reflected Ray
Angle of Angle of
incidence reflection
Plane Mirror

4. The Law of Reflection
The Law of Reflection states that for a plane mirror:
Angle of Incidence = Angle of Reflection
Incident Ray Normal Reflected Ray
Angle of Angle of
incidence incidence
Plane Mirror

5. Images In A Plane Mirror
Light rays reflect off a plane mirror in a regular way.
Angle of the light = Angle to come from
This makesIncidence rays seemof Reflection
behind the mirror at an equal distance..
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.

6. Forming A Virtual Image
Virtual Image
Upright
Same Size
Reversed

7. Concave Mirrors
Concave mirrors have surfaces that curve inward.
A concave mirror reflects light rays so that
they converge (meet) at a certain point.
We call this point the
focal point of the mirror.

8. Concave Mirrors
Concave mirrors form images in 2 different ways.
The type of image depends on the distance
the object is placed from the focal point.
Focal Point

9. 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

10. Convex Mirrors
Convex mirrors have surfaces that curves outward.
A convex mirror reflects light rays
so that they diverge (spread out).
The light rays do NOT
meet at a focal point
in front of the mirror.

11. Convex Mirrors
Convex mirrors ALWAYS form images the same way.
A convex mirror forms a virtual image
that is smaller than the true object.
Focal Point

12. Refraction
Refraction is when light rays are bent.
When light rays pass from one material to
another, the light rays refract (bend).
The rays change direction
where the 2 materials meet.
The light bends because it
changes speed in different
materials (mediums).

13. Refraction
Medium 1 - Air
Light travels fast
Medium 1 - Water
Light travels slow

14. Index of Refraction
Some mediums refract light rays more than others.
This is described by the index of refraction.

15. Index of Refraction
Some mediums refract light rays more than others.
This is described by the index of refraction.

16. Index of Refraction
Some mediums refract light rays more than others.
This is described by the index of refraction.

17. Index of Refraction
Indexes of Refraction for Common Materials
Vacuum 1.00
Air 1.01
Water 1.33
Glycerine 1.47
Glass 1.52
Diamond 2.42

18. Lenses
A lens is a curved device that refracts light precisely.
Lenses are useful because they can
refract light rays in a predictable way.
There are 2 types of lenses:
Concave Convex

19. Concave Lens
A concave lens is thinner in the middle.
A concave lens bends parallel light
rays to make them diverge.
Produce a
virtual image
only

20. Convex Lens
A convex lens is thicker in the middle.
A convex lens bends parallel light rays
so that they meet at a focal point.
Produce a
real or a
virtual image

21. Lenses
Lenses have many uses.

22. Any Questions?