light refraction chapter 29 in textbook
DESCRIPTION
Light is a form of energy. Light travels in a straight line Light speed is 3.0 x 10 8 m/s Light is carried by photons Light can travel through a vacuum Light is a transverse wave Light is an electromagnetic waveTRANSCRIPT
Light refraction Chapter 29 in textbook.
Youll want paper for your notes. Light is a form of energy.
Light travels in a straight line Light speed is 3.0 x 10 8 m/s
Light is carried by photons Light can travel through a vacuum Light
is a transverse wave Light is an electromagnetic wave
ELECTROMAGNETIC WAVES
Electromagnetic waves are waves that are capable of traveling
through a vacuum. They consist of oscillating electric and magnetic
fields with different wavelengths. The Electromagnetic
Spectrum
Increasing frequency Increasing wavelength Increasing Energy The
wave speed equation is: c =f
where c is the speed of light. When light strikes an object it can
be REFLECTED, TRANSMITTED or ABSORBED.
Objects are TRANSPARENT, TRANSLUCENT AND OPAQUE to light
Ultraviolet light oscillates at too high a frequency for electrons
in glass molecules, while infrared is too low. Visible light is
just right. Making glass transparent to visible light and opaque to
infrared and ultraviolet REFRACTION The bending of a ray of light
as it passes from one medium to another is called refraction.
Reflection and Refraction at an Interface The speed of light c in a
material is generally less than the free-space velocity c of 3 x108
m/s. In water light travels about three-fourths of its velocity in
air. Light travels about two-thirds as fast in glass. The ratio of
the velocity c of light in a vacuum to the velocity v of light in a
particular medium is called the index of refraction, n for that
material. Light bends toward the normal when entering medium of
higher index
of refraction Light bends away from the normal when entering medium
of lower index of refraction SNELLS LAW The ratio of the sine of
the incident angle to the sine of the refracted angle is constant.
n1 sin1 = n2 sin2 n1 = index of refraction of the incident medium
n2 = index of refraction of the second medium Example A ray of
light travels from air into liquid
Example A ray of light travels from air into liquid. The ray is
incident upon the liquid at an angle of 30. The angle of refraction
is 22. a. What is the index of refraction of the liquid? n1 = 1 1 =
30 2 = 22 n1 sin 1 = n2 sin 2 = 1.33 Critical Angle n1 sin q1 = n2
sin q2 = n2 sin 90 sin q1 = n2 / n1 = 41 Example Find the critical
angle for an air-crown glass boundary.
ni= 1.52 nr= 1 = 41 Light refraction THIN LENSES Lenses are an
essential part of telescopes, eyeglasses, cameras, microscopes and
other optical instruments. A lens is usually made of glass, or
transparent plastic. The two main types of lenses are convex and
concave lenses.
The focal length (f) of a lens depends on its shape and its index
of refraction. A converging (convex) lens is thick in the center
and thin at the edges.
A diverging (concave) lens is thin in the center and thick at the
edges. Two types of Images A real image is a representation of an
object (source) in which the perceived location is actually a point
of convergence of the rays of light that make up the image. A real
image is visible on the screen and inverted Andformed on the
opposite side of a lens.. A virtual image is an image in which the
outgoing rays from a point on the object never actually intersect
at a point.Virtual images cannot be seen on a screen and form on
the same side of a lens. IMAGE FORMATION BY LENSES
There are three principal rays to locate an image. Ray 1. A ray
parallel to the axis passes through the second focal point F2 of a
converging lens or appears to come from the first focal point F1 of
a diverging lens. Ray 2. A ray which passes through the first focal
point F1 of a converging lens or proceeds toward the second focal
point F2 of a diverging lens is refracted parallel to the lens
axis. Ray 3. A ray through the geometrical center of a lens will
not be deviated. Principal Rays A real image is always formed on
the side of the lens opposite to the object. A virtual image will
appear to be on the same side of the lens as the object. 23.7 Find
the images formed by the following lenses using the Ray Tracing
method. b. Write the characteristics of each image: -real or
virtual, -larger, smaller or same size as object and -upright or
inverted. CASE 1: Object is beyond 2F
Image is real, reduced, inverted and located between f and 2fon the
opposite side of the lens CASE 2: Object at 2F Image is real, same
size, inverted and located at 2f CASE 3: Object between F and
2F
Image is real, magnified, inverted and located beyond 2f CASE 4:
Object is at the focal point
No image is formed. CASE 5: Object is between f and the lens
The image is virtual, upright, magnified and located on the same
sides as the object DIVERGING OR CONCAVE LENS
Case 1: Object outside of 2f Image is virtual, reduced, upright and
located on the same side of the lens as the object Case 2: Object
between f and the lens
Image is virtual, reduced, upright and located on the same side of
the lens as the object What if there are TWO lenses? THE LENS
EQUATION The lens equation can be used to locate the image: Where
do is the objects distance, di is the image distance andfis the
focal length. The ratio M is called the magnification, ho is the
objects size and hi is the image size. 23.8 A 5 cm tall object is
located 30 cm from a convex lens of 10 cm focal length.
a. Find the location and nature of the image. do = 30 cm f = 10 cm
= 15 cm, real ho = 5 cm b. What is the height of the image? = cm,
inverted Sign rules R f do di ho hi radius of curvature +
converging
- diverging f focal length do object distance + real object di
image distance + real images - virtual images ho object size + if
upright - if inverted hi image size Sign rules VISION PROBLEMS:
MYOPIA is when image is formed in front of retina and is also known
as nearsightedness and is corrected with a concave lens VISION
PROBLEMS: HYPEROPIA is when image is formed behind the retina and
is also known as farsightedness and is corrected with a convex lens
VISION PROBLEMS: ASTIGMATISM is when the eye is shaped like a
football rather than the normal eye that has a round shape similar
to basketball. It causes certain amounts of distortion or pitched
images because of the uneven bending of light rays entering the
eye.