PhysicsLAB Review
Spherical Lens Properties

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  Converging Lenses Diverging Lenses
lens shape "caved in" "bowed out"
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
equation
1/do + 1/di = 1/f
do is always positive
di is positive if real
di is negative if virtual
f is positive (convex)
1/do + 1/di = 1/f
do is always positive
diis always negative (virtual)
f is negative (concave)
magnification
equation
M = | di / do | = | I / O | M = | di / do | = | I / O |
image
properties
image properties vary with object's position
sample 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
sample ray diagrams

do di = -f
virtual
M 0
any do < ∞ 0 < di < -f
virtual
M < 1
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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