Transcript Unit 4 Waves Ch. 22 Sec. 3 Reflection & Mirrors Reflected Light • Reminder… – reflection is when a wave strikes a surface & bounces off –

Unit 4
Waves
Ch. 22 Sec. 3
Reflection & Mirrors
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
Parts of the Law of Reflection
1. normal - an imaginary line
perpendicular to the
surface where light rays
strike
2. angle of incidence created by the incoming
light & the normal
3. angle of reflection created by the reflected
light & the normal
Law of Reflection
• law of reflection - angle of incidence = angle of
reflection
(no matter what surface is reflecting the light)
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)
Reflection from Surfaces
Rough Surfaces
Smooth Surfaces
• reflected light goes in many • reflected light goes in a
directions creating a
single direction creating a
diffuse reflection
regular reflection
Reflections from Mirrors
• reflections from a plane mirror (flat)
are…
1) reversed (left & right)
2) seem to come from behind the mirror
Reflections from Mirrors
Convex 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 Mirrors
• concave mirror - surface
is curved inward
– causes light rays to come
together (converge)
– used in headlights &
flashlights
Optical Axis
• optical axis - an imaginary line that is
perpendicular to the center of a convex or
concave mirror
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
Convex Mirror Images
• LIKE a plane mirror…
1. the image in a convex mirror
seems to be behind the mirror
2. the image is always upright
• UNLIKE a plane mirror
(& a concave mirror)…
– the image in a convex mirror is
always smaller than the object