PhysicsLAB

Review
Mirrors


Mirror Physlet
 
  Plane Mirrors Concave Mirrors Convex Mirrors
shape flat mirror "caved in" "bowed out"
radius R   R = 2f R = 2f

position of principal focus

  - - - - F is "in front of the mirror" F is "behind of the mirror"
image
position
di = - do 1/do + 1/di = 1/f
do is always positive
d
i is positive if real
d
i is negative if virtual
f is positive if concave
1/do + 1/di = 1/f
do is always positive
d
i is negative if virtual
f is negative if convex
image
properties
virtual
upright
M = 1
six case ray diagrams
image varies with do
do di = f
real
M 0
do > 2f 2f < di < f
real
M < 1
do = 2f di = 2f
real
M = 1
2f < do < f di > 2f
real
M > 1
do = f no image
is formed
- - - -
do < f 0 < di < -
virtual
M > 1
ray diagrams
virtual, upright, M < 1 
do di = -f
virtual
M 0
any
do <
0 < di < -f
virtual
M < 1
magnification M = 1 M = | di / do | = | I / O | M = | di / do | = | I / O |
rays line up the top/bottom of the eye with the image, draw in a line - solid in the air, dotted behind the mirror, bounce it back to the object.  Then put arrows pointing away from the object, to the mirror, and then into the eye. #1  top of the object, parallel to the axis, strikes the mirror, reflects through F

#2 top of the object, through C, strikes the mirror, reflects back through C

#3 top of the object, passes through F, strikes the mirror, reflects parallel to the axis

#1  top of the object, parallel to the axis, strikes the mirror, lines up with F, reflects back
(dot in line to F)

#2 top of the object, aims for C, strikes the mirror, reflects back (dot in line to C)

#3 top of the object, aims for F, strikes the mirror, reflects parallel to the axis
(dot back parallel reflection)

multiple images of angled plane mirrors N = (360 / q) - 1 drop a normal to the first
subscripted mirror
measure di  = - do
draw in the standard rays
- - - -



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Catharine H. Colwell
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PhysicsLAB

Mainland High School
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