lenses and mirrors. how does light interact with pinholes? how does light interact with lenses?...
TRANSCRIPT
Lenses and Mirrors
• How does light interact with pinholes?
• How does light interact with lenses?–___________
• How does light interact with mirrors?–___________
We can use the _____________.
Refraction
Reflection
photon model
Pinholes
• A ________ can be used to form an image.
Light rays from point source screen
pinhole
Image formation with a Pinhole camera
Image is _______ if pinhole is larger
Image is ________ if pinhole is smaller
Image is __________ is pinhole is smaller
Light source
Dark room = Camera
dimmer
sharper
fuzzy
Mirrors
• Flat
• Concave
• Convex
The Law of Reflection
For reflection the _____________ i equals the _______________ r
i r
The angles are measured relative to the _________, shown here as a dotted line.
incident anglereflected angle
normal
Forming Images with a Plane MirrorA mirror is an object that reflects light. A _______
mirror is simply a flat mirror. Consider an object placed at point P in front of a
plane mirror. An image will be formed at point P´ behind the mirror.
do diFor a plane mirror:
do = -di and ho =hi
hohi
do = distance from object to mirror
di = distance from image to mirror
ho = height of object
hi = height of image
plane
Images
An image is formed at the point where the rays of light leaving a single point on an object either _________ intersect or from where they ________ to originate.
actuallyappear
Images
• If the light rays actually do intersect, then the image is a __________. If the light only appears to be coming from a point, but is not physically there, then the image is a _____________.
real image
virtual image
Images
• We define the ____________, m, of an image to be:
o
i
o
i
d
d
h
hm
heightobject
height image
If m is negative, the image is inverted (upside down).
magnification
Spherical MirrorsA _________ _______ has a surface shape with radius of curvature R. There are two types of spherical mirrors: _______ and _______.
________
________
sphericalmirror
concaveconvex
concave
convex
Focal PointWhen ________ rays (e.g. rays from a distance source) are incident upon a spherical mirror, the reflected rays ________ at the _________ F, a distance R/2 from the mirror.
For a ________ _______, the focal point is in front of the mirror (_____).
parallel
intersect focal point
concavemirror
real
Focal Point
The incident rays ______ from the _______ _______, but they trace back to the focal point F.
For a ____________, the focal point is behind the mirror (________).
convex mirror
virtual diverge
convexmirror
Focal Length
The _______________is the distance from the surface of the mirror to the focal point. It can be shown that the focal length is half the radius of curvature of the mirror.
Sign Convention: the focal length is negative if the focal point is behind the mirror.
For a concave mirror, f = ____
For a convex mirror, f = ___ (R always +)
focal length (f)
½ R
½ R
Ray Tracing
It is sufficient to use ______ principal rays to determine image location. The parallel ray (P ray)
reflects through the focal point. The focal ray (F ray) reflects parallel to the axis, and the center-of-curvature ray (C ray) reflects back along its incoming path.
three
Ray Tracing – Examples
concave convex
Virtual imageReal image
Put film here for
Sharp image.
Lenses
• Concave
• Convex
–Refraction
Reflection and RefractionWhen a light ray travels from one medium to
another, part of the incident light is _________ and part of the light is _____________ at the boundary between the two media.
The transmitted part is said to be __________ in the second medium.
incident ray reflected ray
refracted ray
reflectedtransmitted
refracted
Red Light
Red Light
Red Light
Lenses
Light is reflected from a mirror. Light is __________ through a lens.
refracted
Focal PointThe ___________ of a lens is the place where
parallel rays incident upon the lens ________.
_______________ ______________
focal pointconverge
Diverging lensConverging lens
Ray Tracing for Lenses
P ray travels parallel to the principal axis until lens, it refracts to pass through the focal point on the far side of the lens. The F ray passes through the focal point on the near side of the lens, leaves parallel to the principal axis. The M ray passes through the middle of the lens with no deflection.
Just as for mirrors we use three “easy” rays to find the image from a lens.
Focal Length
• http://www.physics.odu.edu/hyde/Teaching/Spring04/Lectures/318,1,Chapter 26: Geometrical Optics