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Ch 36 Image Formation
"o" is the object that's
being reflected (imaged)
by the mirror. "i" is the
image. "p" is the perpen
dicular distance from the
mirror to the object, and
"q" is the perpendicular
distance from the image
to the mirror.
For a plane mirror:
p = q (image is located the same distance from
the mirror as the object)
and the object & image lie on the same perpendicular to
the mirror.
Images formed by a plane mirror are virtual.
Note that mirrors don't reverse images lefttoright, but
do reverse images fronttoback.
36.2 Images Formed by Spherical Mirrors A spherical mirror is shaped like part of a sphere.
We will consider paraxial rays, those that make a small angle with the principal axis.
A concave mirror reflections are off the "inside" of the mirror, the same side as C. For a concave mirror, rays that are || to the principal axis all reflect through a single focal piont, F, midway between C & V.
The focal length, f, of the mirror is the distance from V to F (or from C to F). Thus,
f = R/
For the relationship between the object's location & its image location, consider the angle α:
Example: Where is the image formed when an object is
placed 50.0 cm in front of a concave mirror whose radius of
curvature is 20.0 cm?
b) What's the magnification of the image; if the object is 2.
cm tall, how big is the image?
Ray Diagrams
or
Locating images by ray tracing:
Rules for rays for a concave (convex) mirrors
A ray || to principal axis is reflected through (from) F.
A ray through (toward) F is reflected out || to the principal
axis.
- A ray through (toward) C is reflected back on itself.
Ch 37 Interference & Diffraction
37.1 Conditions for Interference
a) coherent source the waves that are interfering must maintain a constant phase relationship. b) monochromatic the waves must all be of the same f or λ.
37.2 Young's DoubleSlit Experiment (1801)
diffraction the spreading of a wave as it passes an opening or edge of the scale as the wavelength.
We'll have constructive interference (bright spot or "maximum") when:
We'll have destructive interference (dim spot or "minimum") when:
