Download Document

Chapter Menu
Lesson 1: What is light?
Lesson 2: Light and Matter
Lesson 3: Using Lenses
Lesson 4: The Eye and Vision
Click on a hyperlink to view the corresponding lesson.
11.1 What is light?
wavelength
frequency
medium
electromagnetic spectrum
11.1 What is light?
Light Transfers Energy
• Similar to water waves, light waves also
carry energy from place to place.
11.1 What is light?
Parts of a Wave
• The distance between
any two crests of any
two troughs is the
wavelength.
11.1 What is light?
Frequency and Wavelength
• The frequency of a
wave is the number of
wavelengths that pass a
given point in one
second.
• As the frequency of a
wave increases,
wavelength decreases.
11.1 What is light?
Electromagnetic Waves
• The substance through which a wave moves
is called the medium.
• Light is an
electromagnetic
wave, which is a
type of wave that
can travel in
empty space as
well as in matter.
11.1 What is light?
A Range of Wavelengths
• The electromagnetic spectrum includes all
electromagnetic waves.
• It is arranged in order, from those with the
longest wavelengths to those with the
shortest wavelengths.
• Frequency increases as wavelength
decreases, and is arranged in order of
increasing frequency.
11.1 What is light?
Visible Light
• The visible light spectrum is the range of
electromagnetic waves human eyes can
detect.
• Visible light wavelengths are measured in
nanometers (nm).
• The wavelengths range from 700 nm to
400 nm.
11.1 What is light?
11.1 What is light?
What is the amplitude of a wave?
A distance from crest
to crest
B distance from crest
to trough
C distance from crest
to resting position
D wavelength x frequency
0%
0%
D
0%
C
0%
B
A
B
C
D
A
1.
2.
3.
4.
11.1 What is light?
What is a wavelength?
A the distance from
crest to trough
B the distance from crest
to the rest position
C the distance from
crest to crest
0%
0%
0%
D
0%
C
D the opposite
of frequency
B
A
B
C
D
A
1.
2.
3.
4.
11.1 What is light?
What is the term for the substance
through which a wave moves?
A medium
B substrate
C water
D vacuum
0%
0%
D
0%
C
0%
B
A
B
C
D
A
1.
2.
3.
4.
11.2 Light and Matter
absorption
transmission
scattering
refraction
law of reflection
11.2 Light and Matter
The Interaction of Light and Matter
• When light rays hit matter, they can be
absorbed, reflected, or pass through the
matter.
• All electromagnetic waves, including light,
transfer energy from one place to another.
11.2 Light and Matter
Absorption of Light
• Absorption occurs when light rays hit a
material, and some of the rays’ energy is
transferred to the atoms in the material.
• The transfer of energy
can cause the
temperature of the
material to increase.
11.2 Light and Matter
Transmission of Light
• Transmission occurs when light waves
strike a material and pass through it, such
as with glass.
• Whether the light
waves are transmitted
or absorbed depends
on the wavelength of
the light waves.
11.2 Light and Matter
Scattering of Light
• Scattering occurs
when a material
causes light waves
traveling in one
direction to travel in
all directions.
11.2 Light and Matter
Opaque, Transparent, and
Translucent Materials
• The three candleholders are made of
different materials that absorb, transmit,
and scatter light in different ways.
11.2 Light and Matter
The Speed of Light in
Different Materials
• No object or wave can
move faster than the
speed of light in empty
space.
• When light waves
travel in matter, they
move more slowly.
11.2 Light and Matter
Refraction
• Refraction occurs when a light ray
changes direction when it moves from one
material to another.
11.2 Light and Matter
Refraction and Speed Changes
• Light waves change direction—refract—
when they change speed moving from one
medium to another.
Refraction and Speed Changes (cont.)
11.2 Light and Matter
The Visible Spectrum
• White light is a combination of all light waves
in the visible light spectrum.
• Almost any color of
light can be made
by mixing the three
primary colors—red,
green, and blue—in
different amounts.
The Visible Spectrum (cont.)
11.2 Light and Matter
11.2 Light and Matter
Reflection
• According to the law of reflection, when a
light ray is reflected from a surface, the angle
of incidence equals the angle of reflection.
11.2 Light and Matter
Regular and Diffuse Reflection
• Light ray reflected from an uneven surface
hits a spot in the surface that is at a slightly
different angle, causing the rays to go in
many different directions.
• Diffuse reflection is the reflection of light rays
from a rough surface.
11.2 Light and Matter
Regular and Diffuse Reflection (cont.)
• The smooth surface of a mirror reflects
parallel light rays so that they remain
parallel.
• This is called regular reflection.
11.2 Light and Matter
Reflection and Color
• As white light strikes and
object, some of the light is
absorbed and some is
reflected.
• The reflected light enters
your eyes and causes you
to see the object.
Color
11.2 Light and Matter
What is the term for the process of
transferring light energy to the
molecules in a material?
A transmission
B absorption
C scattering
D refraction
0%
0%
D
0%
C
0%
B
A
B
C
D
A
1.
2.
3.
4.
11.2 Light and Matter
Which of the following does light
travel fastest through?
A transparent objects
B empty space
C air
D water
0%
0%
D
0%
C
0%
B
A
B
C
D
A
1.
2.
3.
4.
11.2 Light and Matter
Why does an object appear to be blue?
A it absorbs the blue
wavelength
B it scatters the blue
wavelength
C it reflects all the other
colors except blue
0%
0%
0%
D
0%
C
D it absorbs all the
wavelengths except blue
B
A
B
C
D
A
1.
2.
3.
4.
11.3 Using Lenses
lens
convex lens
focal point
focal length
11.3 Using Lenses
What is a convex lens?
• A lens is a transparent object with at least
one curved side that causes light waves to
bend.
• A convex lens is a lens that bulges
outward.
– Convex lens: parallel light rays are bent
so they come together, or converge
– Concave lens: parallel light rays spread
apart, or diverge
11.3 Using Lenses
What is a convex lens? (cont.)
• A concave lens is thinner in the middle than
at the edges.
11.3 Using Lenses
Light’s Path Through a Convex Lens
• A light ray bends when it slows down
moving from air into the lens.
• The light ray bends again when it speeds
up moving from the lens back into the air.
11.3 Using Lenses
Focal Point and Focal Length
• The focal point is the point where all of the
beams of light converge.
• In a convex lens, all light rays traveling
parallel to the optical axis are bent so that
they pass through the focal point.
11.3 Using Lenses
Focal Point and Focal Length (cont.)
• The focal length is the distance from the
center of the lens to the focal points.
11.3 Using Lenses
Image Formation by a Convex Lens
• The image formed by a convex lens depends
on the position of an object relative to the
focal point.
11.3 Using Lenses
Optical Instruments
• An optical instrument uses lenses to focus
light and create useful images.
• Different optical instruments do this by
combining lenses in various ways.
• Types of optical instruments
– Cameras
– Telescopes
– Microscopes
11.3 Using Lenses
Cameras
• A camera is focused by moving various
lenses back and forth until a sharp image
is formed.
• The image is smaller than the object and is
upside down.
• To take a picture, the shutter opens so that
light enters the camera, and film or an
electronic sensor is exposed.
11.3 Using Lenses
Cameras (cont.)
• To control the amount of light that reaches
the film or light sensor, cameras have a
diaphragm or an aperture.
11.3 Using Lenses
Telescopes
• As an object gets farther away, less of the
light from the object enters the openings in
your eyes.
• A telescope is an optical instrument that
makes far-away objects seem closer.
• There are two basic types of telescopes—
refracting and reflecting.
11.3 Using Lenses
Refracting Telescopes
• The objective lens in a refracting
telescope is much larger than the
opening in a human eye.
• Much more light
from a distant
object enters the
objective lens
than would enter
an eye.
11.3 Using Lenses
Reflecting Telescopes
• An image of a distant object is formed
inside the telescope tube when light
rays are reflected from the curved
surface of a mirror.
• The largest
telescopes are
reflecting
telescopes.
11.3 Using Lenses
Microscopes
• The eyepiece lens of a
microscope is positioned
so it is closer to the image
than one focal length.
• This makes the image
enlarged by the objective
lens even larger.
11.3 Using Lenses
Where do all the beams of light
passing through a convex lens
converge?
A focal point
B optical axis
C two focal lengths
from the lens
0%
0%
0%
D
0%
C
D in the center of
the lens
B
A
B
C
D
A
1.
2.
3.
4.
11.3 Using Lenses
What happens to light when it moves
from air into a convex lens?
A it is reflected
B it is scattered
C it slows down
D it speeds up
0%
0%
D
0%
C
0%
B
A
B
C
D
A
1.
2.
3.
4.
11.3 Using Lenses
Which uses a curved mirror to form
an image that is magnified by an
eyepiece lens?
A refracting telescope
B reflecting telescope
C camera
D microscope
0%
0%
D
0%
C
0%
B
A
B
C
D
A
1.
2.
3.
4.
11.4 The Eye and Vision
cornea
pupil
iris
retina
pigment
11.4 The Eye and Vision
How the Eye Forms an Image
• As light enters your
eye, lenses in your
eye focus light to
produce an image on
the back of your eye.
• Special cells at the
back of the eye
convert the image into
electrical signals that
travel to your brain.
11.4 The Eye and Vision
Cornea
• Light enters your eye through the cornea,
which is a clear area of the sclera—the
outer layer of the eye.
The Eye
11.4 The Eye and Vision
11.4 The Eye and Vision
Iris
• The pupil is the dark opening into the
interior of your eye.
• The pupil is surrounded by the iris—the
colored part of your eye behind the cornea.
11.4 The Eye and Vision
Lens
• The lens of your eye is convex and
flexible.
• The ciliary muscles attached to the lens
change its shape depending on the distance
of the object being looked at.
11.4 The Eye and Vision
Retina
• The retina is a sheet of light-sensitive
cells in the back of the eye.
• Rod cells respond to dim light and cone
cells enable you to see colors.
11.4 The Eye and Vision
11.4 The Eye and Vision
Seeing Color
• The response of cone cells to different
wavelengths of light cause you to see
objects as having color.
• Three types of cone cells:
– One responds to the wavelengths of red and
yellow light, causing you to see red.
– One responds to yellow and green light, causing
you to see green.
– One responds to blue and violet light, causing
you to see blue.
11.4 The Eye and Vision
Pigment Colors
• A pigment is a material used to change
the color of other materials or objects.
• The color of a pigment depends on the
wavelengths of the light it reflects.
11.4 The Eye and Vision
Pigment Colors (cont.)
11.4 The Eye and Vision
Color Printing
• The pictures in magazines are formed
by many tiny dots of color.
• Usually, the primary colors of pigments, as
well as black, are used.
11.4 The Eye and Vision
Common Vision Problems
• Color deficiency: either lack red or green
cones, or the cones do not function
correctly
11.4 The Eye and Vision
Common Vision Problems (cont.)
• Nearsightedness: cannot see faraway
objects clearly
11.4 The Eye and Vision
Common Vision Problems (cont.)
• Farsightedness: cannot see nearby
objects clearly
How are lenses
used to correct
vision?
11.4 The Eye and Vision
What controls the amount of light
that enters your eye?
A ciliary muscles
B cornea
C sclera
D iris
0%
0%
D
0%
C
0%
B
A
B
C
D
A
1.
2.
3.
4.
11.4 The Eye and Vision
What part of the eye enables you to
see colors?
A pupil
B rod cells
C cone cells
D optic nerve
0%
0%
D
0%
C
0%
B
A
B
C
D
A
1.
2.
3.
4.
11.4 The Eye and Vision
Which describes a nearsighted eye?
A it is missing some cone
cells or the cones don’t
function properly
B the eyeball is too short
for the lens to form a
clear image
D the eyeball is too long for
the lens to form a clear image
0%
0%
0%
D
0%
C
C the rods at the back of
the eye do not function
properly
B
A
B
C
D
A
1.
2.
3.
4.