1. Let there be ...
Light

2. Two theories could explain
The Nature of Light
What is Light?
By the 17th century,
light had been observed to…
1. travel in straight lines
2. reflect
3. refract
4. transmit energy from
one place to another
Two theories could explain
these phenomena.

3. The WAVE THEORY,
advocated by
Christian Huygens
and Robert Hooke,
said that light was a wave.
The PARTICLE (corpuscular) THEORY, advocated by Isaac Newton and later by Pierre Laplace, said
that light was made up of a stream
of tiny particles
called corpuscles.

5. Light is ... This leads us to the Duality Principle:
a wave when it acts like a wave
a particle when it acts like a particle

6. Visible light is that portion of the
electromagnetic spectrum which stimulates the retina of the
human eye.
Visible spectrum
wavelengths range
from about 400 nm (violet) to 760 nm (red).
Light travels at about 3 x 108 m/s through
empty space and slightly slower through air.
Remember that for all waves, v = f.

7. COLOR can clearly see objects through them
Materials may be classified as:
transparent - readily transmits light;
can clearly see objects through them
translucent - transmits, but diffuses, light;
cannot see objects clearly through them
opaque - transmits no light;
cannot see through them

8. WHITE light is composed of all colors.
Red, orange, yellow, green, blue, violet
is the order of
increasing frequency
or decreasing wavelength.
Frequencies directly above this spectrum are
ultraviolet.
Frequencies directly below this spectrum are
infrared.

9. The color of an opaque object depends
on the colors (frequencies) of light
incident upon it and on the colors
(frequencies) of light reflected.
The color of a transparent object depends
on the colors (frequencies) of light
incident upon it and on the colors
(frequencies) of light transmitted.

10. colors that combine to form white light.
Complimentary colors are two
colors that combine to form white light.
Red and cyan,
blue and yellow,
green and magenta
are pairs of complimentary colors.
Red, blue, and green are called
primary colors or secondary pigments.
Cyan, yellow, and magenta are called
primary pigments or secondary colors.

11. POLARIZATION
Only transverse waves
may become polarized.

13. air water As light reaches the boundary between two media,
its energy is partially reflected back and
partially transmitted into the new medium.
The amount that is reflected
depends on the types of materials and
the angle of incident rays.
air
water

14. Laws of Reflection First Law Second Law The angle of incidence, i, is
equal to the angle of reflection, r. n i r
Second Law
The incident and reflected rays,
and the normal, are coplanar.

15. Images formed by mirrors and lenses
may be classified as real or virtual.
Real Image
formed by actual rays of converging light
Virtual Image
not formed by actual rays of converging
light, but from where the rays of light
appear to come (diverging light rays)

16. Plane Mirror Images 1. virtual 2. upright 3. same size as object
Images formed by plane mirrors are always:
1. virtual
(virtual images are always behind mirrors)
2. upright
(virtual images are always upright)
3. same size as object
(if the image is larger or smaller, the mirror isn’t flat)
4. front and back are reversed
(some say “left and right”)
5. located as far behind the mirror
as the object is in front

18. Curved Mirrors Terminology center of curvature - C; the
center of the original sphere
radius of curvature - r;
distance from center of curvature to the mirror
vertex - V; the center of the mirror
principal axis - a line through C and V
principal focus - F; the point on the
principal axis where light rays parallel
and close to the principal axis converge;
or from where they appear to diverge
focal length - f; distance from V to F

19. Ray Diagrams Concave (Converging) Mirrors
rays parallel and close to the principal
axis reflect through the focus
2. rays passing through the focus reflect
parallel to the principal axis
3. rays passing through the center of
curvature reflect straight back along
the incident path
C F

20. Convex (Diverging) Mirrors
1. rays parallel and close to the principal
axis reflect away from the focus
2. rays heading toward the principal focus
reflect parallel to the principal axis
3. rays heading toward the center of
curvature reflect straight back along
the incident path
F C

21. di/do = si/so 1/f = 1/do + 1/di Mirror Equation Magnification
Diverging rays must be extended as dotted lines
behind the mirror in order to locate some images.
Mirror Equation
Magnification
di/do = si/so
1/f = 1/do + 1/di
f = focal length; positive for converging
mirrors, negative for diverging mirrors
do = object distance; usually positive
di = image distance; can be positive or negative
so = object size (height)
si = image size (height)

22. Images formed by concave (converging) mirrors may be:
1. real, virtual, or non-existent
2. upright or inverted
3. reduced, enlarged, or same size
4. in front or behind the mirror
The image properties depend on the
object’s location with respect to the
mirror, focus, and center of curvature.

23. object is beyond the center of curvature:
image is real, inverted, and reduced
object is on the center of curvature:
image is real, inverted, and the same size
object between center of curv. and focus:
image is real, inverted, and enlarged
object is on the focus:
no image; rays reflect parallel
object is inside the focus:
image is virtual, upright, and enlarged

24. 4. located behind the mirror between the vertex and focus
Images formed by convex (diverging) mirrors are always:
1. virtual
2. upright
3. reduced
4. located behind the mirror between the
vertex and focus

25. General Image Trends real images are always inverted
virtual images are always upright
real images are always in front
of the mirror
virtual images are always
behind the mirror
negative image distance means
virtual image
positive image distance means
real image