Transcript Refraction and Its Uses

Yu Zhuoxin
3P3 28
Refraction
What does refraction
mean
Definition of refraction
 Refraction is the bending of light as it passes from one
substance to another. The bending is caused by the
differences in density between the two substances.
Eg
Uses of refraction
 Camera
 Microscope
 Magnifying glass
 overhead projector
 Telescope
 …………
Camera
The window--technically
called the aperture--is covered
with a ground-glass lens for
focusing the light that enters
the camera. Between the lens
and the window is a shutter
that opens to let light into the
camera body. The
photographic medium is the
film on which the light image
is recorded.
Camera-how do light refract?
 making an image
 To make the image, you need to use lenses, and
fancier cameras have fancier lense systems to get
better images. To actually get an image where the
film is, the lenses take the incoming light and
focus it there.
 A majority of cameras have a lens positioned in
front of the camera's opening to gather the
incoming light and focus all or part of the image
on the recording surface. The light can be focused
as light bents when they enters the lens. This is
due to the reflection of light.
Camera
Microscope
A microscope is an
instrument to see objects
too small for the naked
eye, such as cells, bacteria
and even atoms
There are many different
types of microscopes .
Actually, some microscopes
do not work on the
phenomenon of refraction.
Microscope
 light waves being bent as they travel
through glass. In a microscope, the
idea is to bend diverging (spreadingout) light into a parallel path, then
bend that parallel-path light into a
small focus at the eye, and there is a
magnitude image formed.
Microscope
 The object is placed between f and 2f. The total
magnification is determined by the product of the
magnification of the eyepiece and the magnification of
the objective. The magnification of the eyepiece and
the magnification of the objective must be calculated
separately. There are two basic equations involved in
finding the magnification. The first is 1/f=1/di + 1/do,
and the second is di/do = si/so = magnification.
Diagrams
diagrams
Magnifying glass
A magnifying glass is
simply a convex lens
meant to be held up to
an object to see it
magnified. It is a very
simple form of
microscope.
how magnifying glass works
 The magnifying glass is not projecting an image
onto anything; it is merely bending the Light rays
from the object so that the object will appear larger.
 the object is between the center of the lens and F,
and the image is magnified, virtual and upright,
and on the same side. This is why a magnifying
glass only works when it is close enough to the
object (because the object must be between the
center and F).
how magnifying glass works
Magnifying glass,
namely convex
lens
image
object
Eye sight
Telescope
Telescopes are devices that
are endowed with magnifiers
to allow you to see things
magnified with a clear view.
Telescopes are commonly
used in science or its
branches, particularly
astronomy and physics.
Telescope
 As the light rays travel through the
lenses of the telescope, they are
refracted.
 In a telescope, the idea is to bend
parallel light from very faraway objects
into a small focus at the eye so that a
sharp and clear image can be formed at
the back of the eye.
Diagrams
Diagrams
overhead projector
An overhead projector
typically consists of a
large box containing a
very bright lamp and a
fan to cool it. On top
of the box is a large
fresnel lens that
collimates the light.
overhead projector
 The light from the lamp travels through the
transparency and into the mirror where it is shone
forward onto a screen for display. The mirror allows
both the presenter and the audience to see the image
at the same time, the presenter looking down at the
transparency as if writing, the audience looking
forward at the screen. The height of the mirror can
be adjusted, to both focus the image and to make the
image larger or smaller depending on how close the
projector is to the screen.
reference
 http://morningnoonandnight.files.wordpress.com/200
7/09/spectacles.jpg
 http://en.wikipedia.org/wiki/Glasses
 http://en.wikipedia.org/wiki/File:Myopia.svg
 http://www.phys.ufl.edu/~avery/course/3400/camera/
camera_image_landscape.jpg
 http://otherbrooksbrother.files.wordpress.com/2008/0
2/microscope.jpg
 http://www.ehow.com/how-does_4574398_cameraswork.html
 http://wiki.answers.com/Q/How_is_refraction_used_i
n_your_every_day_life
reference
 http://www.wisegeek.com/how-does-a-magnifying-
glass-work.htm
 http://en.wikipedia.org/wiki/Overhead_projector
 http://www.topbits.com/how-overhead-projectorswork.html
Thank you for
your kind
attention