1. Ch. 22 Sec. 3 Reflection & Mirrors
Unit 4 Waves
Ch. 22 Sec. 3
Reflection & Mirrors

2. Reflected Light Reminder…
reflection is when a wave strikes a surface & bounces off
reflected light = an image
light obeys the law of reflection
involves:
1) the normal
2) angle of incidence
3) angle of reflection

3. Parts of the Law of Reflection
normal - an imaginary line perpendicular to the surface where light rays strike
angle of incidence - created by the incoming light & the normal
angle of reflection - created by the reflected light & the normal

4. Law of Reflection
law of reflection - angle of incidence = angle of reflection
(no matter what surface is reflecting the light)

5. Reflection from Rough Surfaces
scattering - when light traveling in one direction is sent in many directions
occurs when light is reflected off a rough surface OR when light encounters small particles (dust)

6. Reflection from Surfaces
Rough Surfaces
Smooth Surfaces
reflected light goes in many directions creating a diffuse reflection
reflected light goes in a single direction creating a regular reflection

7. Reflections from Mirrors
reflections from a plane mirror (flat) are…
reversed (left & right)
seem to come from behind the mirror

8. Reflections from Mirrors
Convex Mirrors
Concave Mirrors
convex mirror - surface is curved outward
causes light rays to spread out (diverge)
can view a larger area
used for security mirrors & side mirrors in cars
concave mirror - surface is curved inward
causes light rays to come together (converge)
used in headlights & flashlights

9. Optical Axis
optical axis - an imaginary line that is perpendicular to the center of a convex or concave mirror

10. Concave Mirror Images
IF incoming light is parallel to the optical axis, all light reflected from a concave mirror passes through the same point = focal point
(distance from this point to the center of
the mirror = focal length)
IF an object is beyond the focal point…
the image will be upside down (inverted)
IF an object is b/w the mirror & the focal point…
the image will be upright

11. Convex Mirror Images LIKE a plane mirror… UNLIKE a plane mirror
the image in a convex mirror seems to be behind the mirror
the image is always upright
UNLIKE a plane mirror
(& a concave mirror)…
the image in a convex mirror is always smaller than the object