Chapter 23 Properties of Light

Section 1: Objectives• Use ray diagrams to show how light is

reflected or refracted.

• Compare plane mirrors, concave mirrors, and convex mirrors.

• Use ray diagrams to show how mirrors form images.

• Describe the images formed by concave and convex

Mirrors and Lenses• Because light waves travel in straight

lines, you can use an arrow called a ray to show the path and the direction of a light wave.

• Rays help to show the path of a light wave after it bounces or bends.

Mirrors and Lenses• A plane mirror is a mirror that has a flat

surface.

• The reflection of an object in a plane mirror is right side up and the same size as the object, but reversed left to right.

• Plane mirrors form virtual images. A virtual image is an image through which light does not travel

Mirrors and Lenses: Figure 1

Mirrors and Lenses• A concave mirror is a mirror that is

curved inward.

• The image formed by a concave mirror depends on the optical axis, focal point, and focal length of the mirror.

Mirrors and Lenses: Figure 2

Mirrors and Lenses• Draw a ray diagram to determine if a

concave mirror will form a virtual image like a plane mirror, or a real image.

• A real image is an image through which light passes.

Mirrors and Lenses: Figure 3

Mirrors and Lenses• A convex mirror is a mirror that

curves outward.

• The image formed by a convex mirror is always virtual, right side up, and smaller than the original object.

Mirrors and Lenses: Figure 4

Mirrors and LensesA lens is a transparent object that

forms an image by refracting, or bending, light.

Two kinds of lenses are convex and concave.

Mirrors and Lenses: Figure 5

Mirrors and Lenses: Figure 6 A convex lens is thicker in the

middle than at the edges.

Mirrors and Lenses: Figure 7A concave lens is thinner in the middle than at the edges.

Chapter 23 Section 1 Recap1) Why are rays useful when studying

light waves?2) What type of images do plane

mirrors form?3)What is the difference between a

virtual and a real image?4) From Figure 1, why does your image

appear to be behind the mirror?5) List 3 things an image formed by a

concave mirror depends on.

Chapter 23 Section 1 Recap6) What type of mirror is depicted in

Figure 3?7) List 3 characteristics of an image

formed by a convex mirror.8) List 2 types of lenses.9) From Figure 4, when light passes

through a concave and convex lens, describe what happens to the rays.

10) Compare and contrast a concave and convex lens.

Section 2: Objectives• Identify the parts of the human eye,

and describe their functions.

• Describe three common vision problems.

• Describe surgical eye correction.

Detecting Light• Your eye gathers visible light to form the

images that you see.

• The thickness of the lens of the eye changes so that objects at different distances can be seen in focus. • The light that forms a real image on the retina is

detected by receptors called rods and cones.

• The next slide explains how your eyes work.

Detecting Light: Figure 1

Detecting Light• Nearsightedness happens when a

person’s eye is too long. A nearsighted person can see something clearly only if it is nearby. • Faraway objects look blurry.

• Farsightedness happens when a person’s eye is too short. A farsighted person can see faraway objects clearly. But things that are nearby look blurry.

Detecting Light: Figure 2The images below explain how

nearsightedness and farsightedness can be corrected with glasses.

Detecting Light• Color Deficiency is another name for

colorblindness. • The majority of people who have color

deficiency can’t tell the difference between shades of red and green or can’t tell red from green.

• Color deficiency happens when the cones in the retina do not work properly.• Color deficiency cannot be corrected.

Detecting Light• Surgical eye correction works by reshaping

the patient’s cornea by using a laser. • Patients often gain perfect or nearly perfect vision

after surgery.

• Some patients report glares, double vision, or trouble seeing at night.

• People under 20 years old should not have surgical eye correction because their vision is still changing.

Chapter 23 Section 2 Recap1) From Figure 1, what is the cornea?2) From Figure 1, what is the iris?3) From Figure 1, what is the function

of the lens?4) From Figure 1, what is the retina?5) From Figure 1, what is the function

of rods and cones?6) What is the major difference

between a nearsighted and farsighted person?

Section 3: Objectives• Describe three optical instruments.

• Explain what laser light is, and identify uses for lasers.

• Describe how optical fibers work.

• Explain polarized light.

• Explain how radio waves and microwaves are used in four types of communication technology.

Optical Instruments• Optical instruments are devices that use

mirrors and lenses to help people make observations.

• Cameras A camera is used to record images. • All cameras have a lens, shutter, and an aperture.

• A 35 mm camera records images on film. • A digital camera uses light sensors to record

images and to send electric signals to a computer.

Optical Instruments: Figure 1

Optical Instruments• Telescopes are used to see detailed

images of large, distant objects.

• Refracting telescopes use lenses to collect light.

• Reflecting telescopes use mirrors to collect light.

Optical Instruments: Figure 2

Optical Instruments• Microscopes are used to study tiny, nearby

objects.

• Microscopes have two convex lenses.

• An objective lens is close to the object being studied.

• An eyepiece lens is in the lens you look through.

Optical Instruments• A laser is a device that produces intense

light of only one wavelength and color.

• The word laser stands for light amplification by stimulated emission of radiation.

• Amplification is the increase in the brightness of the light. • Radiation is energy transferred as

electromagnetic waves.

Optical Instruments: Figure 3

Optical Instruments: Figure 4

Optical Instruments• Lasers are used to make holograms.

• A hologram is a piece of film that produces a three-dimensional image of an object.

• Lasers have many other applications.

• They are used to cut materials such as metal and cloth.

• Doctors sometimes use lasers for surgery. CD players use lasers to read CDs.

Optical Instruments• An optical fiber is a thin, glass wire

that transmits light over long distances.

• Optical fibers are used to transmit information through telephone cables and network computers. • Doctors use optical fibers to see inside

patients’ bodies.

Optical InstrumentsOptical fibers are like pipes that carry

light.

Light stays inside an optical fiber because of total internal reflection, the complete reflection of light light along the surface of the material.

Optical Instruments: Figure 5

Optical Instruments• Polarized light consists of light waves

that vibrate in only one plane.

• Some sunglasses and camera lenses use polarized filters to reduce glare.

Optical Instruments: Figure 6

Optical Instruments• Light waves, radio waves, and microwaves

are all types of electromagnetic waves.• Cordless telephones and cellular telephones

use radio waves and microwaves to send signals.

• The base of a cordless telephone changes the signal it receives into radio waves. • The handset changes the radio waves into

sound.

Optical InstrumentsCellular telephones send and receives

signals from distant towers.

Instead of using radio waves like cordless phones, cellular phones use microwaves to send information.

Optical Instruments• Microwave signals are broadcast from space

to satellite dishes on Earth.

• Satellites allow more people to receive the signals and to receive higher quality signals than if antennas on Earth were used.

• The Global Positioning System The GPS is a network of 27 satellites that orbit Earth.• A GPS receiver receives signals from at least four

satellites to find its exact location.

Optical Instruments: Figure 7

Chapter 23 Section 3 Recap1) List 3 things that all cameras

have.2) How does a 35 mm camera

record images?3) From Figure 1, what is the

function of the shutter?4) From Figure 1, what is the

function of the lens?5) From Figure 1, what is the

function of the aperture?

Chapter 23 Section 3 Recap6) What is the difference

between refracting and reflecting telescopes?

7) From Figure 2, how many convex lenses does a refracting telescope have?

8) How many convex lenses do microscopes have?

9)What is amplification?10) What is radiation?

Chapter 23 Section 3 Recap11) From Figure 3, what is the major

difference between laser light and non-laser light?

12) What is a hologram?13) T/F Cellular phones do not send and

receive signals from distant towers.14) From Figure 7, how many times do

GPS satellites orbit Earth/15) From Figure 7, how many satellites

do GPS receive signals from at one time?