PhysicsLAB

Review
Lenses

Web Resources

Alert: This is a required review activity: 

CP Workbook:  Lens properties

Ray Diagram Labs: 

Converging Lenses (6 cases)
Diverging Lenses (2 cases)


Equations

       

n = c / v        n = lvac / lmed       n1 sin q1 = n2 sin q2        vw = fl


Summary

  Converging Lenses Diverging Lenses
shape "caved in" "bowed out"

position of principal focus

F is "behind the lens"
on the opposite side of the lens as the incoming light
F is "in front of the lens"
on the same side of the lens as the incoming light
image
position
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 (convex)
1/do + 1/di = 1/f
do is always positive
d
i is always negative (virtual)
f is negative (concave)
image
properties
varies with do
six case ray diagrams
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

 

virtual, upright, M < 1
ray diagrams
do di = -f
virtual
M 0
any
do <
0 < di < -f
virtual
M < 1
magnification M = | di / do | = | I / O | M = | di / do | = | I / O |
rays #1 top of the object, parallel to the axis, strikes the lens, refracts through F

#2 top of the object, passes through the center of the lens unbent

#3 top of the object, aims for F', strikes the lens, refracts parallel to the axis

#1 top of the object, parallel to the axis, strikes the lens, refracts through F (dot in line to F)

#2 top of the object, passes through the center of the lens unbent

#3 top of the object, aims for F', strikes the lens, refracts parallel to the axis (dot back refracted ray)




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Catharine H. Colwell
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