Review Spherical Lens Properties
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 < freal M < 1 do = 2f di = 2freal M = 1 2f < do < f di > 2freal M > 1 do = f no image is formed - - - do < f 0 < di < -∞ virtual M > 1

virtual, upright, M < 1
sample ray diagrams

 do ∞ di = -fvirtual M 0 any do < ∞ 0 < di < -fvirtual 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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