Thin lenses  devices
which refract light
converging lenses in air (chart)
thicker in the center than on the edges, convex
converge light  principal focus is to the right
usually form real inverted images (review 6 cases)
(#6) form enlarged virtual upright images when d_{o} < f
(#5) do not form any image when d_{o} = f (parallel rays)
(#4) form real enlarged images when 2f < d_{o} < f
(#3) form real images that are the same size as the object when d_{o} = 2f
(#2) form real reduced images when d_{o} > 2f
(#1) form point images when d_{o} Þ ¥
diverging lenses in air (chart)
thicker on the edges than in the center, concave
diverge light  principal focus is to the left
always form reduced virtual upright images
thin lens equation
d_{o} is always positive with a single lens
d_{i} is positive for real images,
negative for virtual images
f is positive for converging lenses, negative for diverging lenses
magnification
thin lenses in close combination
power of a lens
measured in Diopters
focal length must be measured in meters
Lensmaker's equation
n_{1} is the index of the lens
n_{2} is the index of the surrounding
medium
r_{1} is the radius of curvature for the
front surface (+ if convex,  if concave)
r_{2} is the radius of curvature for the
back surface (+ if convex,  if concave)
K_{shape} represents the shape of the
lens which does not change when placed in different mediums
doublelens systems
when drawing ray diagrams or using the thinlens equation, work each lens separately
remember that the image of lens #1 is the object for lens #2
to calculate d_{o} for lens #2, subtract
d_{i} for lens #1 from the total
distance separating the lenses
the magnifications of the system is the product of the magnifications of each separate
lens
converging/converging and
converging/diverging systems
converging/converging can form a final image that is either real and upright or virtual
and inverted
converging/diverging form virtual inverted images
ray diagram for microscope  virtual image formed by eyepiece
Refraction
index of refraction
c = 3 x 10^{8} m/sec
n > 1
the index is a measure of a medium's optical density (photon interaction with
electrons)
dispersion: a medium's index of refraction is actually frequency dependent
(spectrum)
Snell's Law
light bends towards the normal when it enters a more dense medium
light slows down when its travels through a more dense medium
the wavelength of light decreases as it travels through a more optically dense medium
the frequency of light is an invariant  it never changes
