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Lecture

PHYS 101 Lecture Notes - Spherical Aberration, Virtual Image, Real Image


Department
Physics
Course Code
PHYS 101
Professor
Kenneth Ragan

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Phys 101 Alanna Houston
November 20, 2007
-Primarily see virtual image
-In the example of a real image, you would only see the image
clearly if you were further from the mirror than the image (so your
eye received diverging rays)
-Concave shapes can also be used for other waves (sound mirror)
-Convex mirrors can also use the mirror equation. Focal length is: f
= r/2
-Careful with the sings of distances: f is negative in this case (but
the rest of our sign convention is unchanged)
-A convex right-hand rear view mirror on a car. Radius of curvature
is 16.0 m. What is the image location and magnification for an
object 10.0 m away? Most mirrors like this carry a warning:
“objects in this mirror may be closer than they appear!” Why?
or = 16.0 m
of = -8.0 m
o1/do + 1/di = 1/f
o1/di = -1/8 – 1/10
o-4.44 m = di
om = -4.4 / 10 = +0.44
-You look into a shiny Christmas tree ball (diameter 9.0 cm) from
30.0 cm away. Where is your image? Is it real or virtual? Upright of
inverted?
o1/do + 1/di = 1/f
or = 4.5 cm
of = -2.25 cm
o–1/2.25 = 1/30 + 1/di
odi = -2.09 cm = 2.1 cm
om = -di / do = - -2.1/3.0 = 1/15 = upright
otherefore, virtual and upright
THIN LENSES
-made up of spherical surfaces where the radius of curvature is
large compared to the lens size so we ignore spherical aberration:
that is, we assume that parallel rays are focussed at the focal
point at the focal length f from the lens: look at picture
-look at pictures of converging and diverging lenses.
-With ray tracing, we can draw the position of the image of an
arbitrary object, with rules much the same as those for spherical
mirrored surfaces (see last lectures)
-Rays parallel to the optic axis are refracted through the focal point
F (red ray)
-Rays through the second focal point FINISH
-We can do the same for diverging lens
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