First Law of Thermodynamics Physics 202 Professor Lee Carkner Lecture 13.
Mirrors Physics 202 Professor Lee Carkner Lecture 20.
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Transcript of Mirrors Physics 202 Professor Lee Carkner Lecture 20.
PAL #19 EM Waves Laser from air to glass to water to glass to
air
airn=1
airn=1
glassn=1.52
glassn=1.52
watern=1.33
1 2
34
5
PAL #19 EM Waves To find each angle, n1 sin 1 = n2 sin 2
sin-1 [(n1 / n2 ) sin 1]= 2
Input angle for each eqn is output angle from previous egn
2 = sin-1 [(1 / 1.52 ) sin ] =
3 = sin-1 [(1.52 / 1.33 ) sin ] =
4 = sin-1 [(1.33 / 1.52 ) sin ] =
5 = sin-1 [(1.52 / 1 ) sin ] =
Mirrors
Trace back the reflections of light from object O and it will converge to make image I I is distance i from mirror
Images in the “real world” are called real
Plane Mirror
has curvature of infinity Plane mirror images:
Are the same size as
the object
Are the same distance behind the mirror as the object is in front of it
i = -p Note that distances “in the
mirror” are negative
Spherical Mirrors
The center of curvature (C) is the center of the sphere that the mirror is a section of A distance r from the mirror
The distance to the center of the mirror from the focal point is the focal length (f)
f = ½ r
Concave and Convex Concave mirror:
The center of curvature is in front of
the mirror
The image is larger than the object
Convex mirror: The center of curvature is behind
mirror
The image is smaller than the object
Ray Drawing Can find image properties by drawing
rays from object to image First draw (to scale):
mirror (including curvature) center of curvature (at r)
Follow ray drawing rules for two rays from top of object Where they intersect is top of image
3) A ray that reflects from the mirror at the intersection with the central axis reflects symmetrically about the central axis
Mirror Equation Where are the images and how large are they?
When measuring from the center of the mirror:
i is the distance to the image
when I and F are on the back side of the mirror i and f are negative
1/p + 1/i = 1/f
Magnification If h is the height of the object and h’ is
the height of the image, then the magnification is given by:
|m| = h’/h
m = -i/p For m = 1, image and object are same size For |m| < 1, image is smaller If m is negative, image is inverted
Concave
Produces a upright, virtual image
Concave mirrors are used to provide magnification (e.g. a shaving or make-up mirror)
Produces an inverted, real image
A real image is projected onto something, it is not behind the mirror
Convex
For a convex mirror: The center of
curvature is behind the mirror
The image is closer to the mirror (|i| < p)
The image is smaller than the object
What is the proper equation for I3?
A) ½ I2B) ½ I0 cos2
C) I0 cos2 6cos2 6
D) ½ I0 cos2 cos2 3
E) ½ I0 cos2 6cos2 6
If you removed the middle polarizer, what would be the
intensity I3?
A) 0B) ½ I0 cos2
C) I0 cos2 6cos2 6
D) ½ I0 cos2 cos2 3
E) ½ I0 cos2 6cos2 6
What is the direction of polarization of polarized sunglasses?
A) Left - rightB) Up - downC) At a 45 degree angle to the verticalD) One lens is up-down and one is left
rightE) They could be polarized in any
direction