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Light
Light and Color
Reflection and Mirrors
Refraction and Lenses
Seeing Light
Using Light
Table of Contents
Light - Light and Color
When Light Strikes an Object
When light strikes an object, the light can be reflected, transmitted, or absorbed.
Light - Light and Color
The Color of Objects
The color of an opaque object is the color of the light it reflects.
Light - Light and Color
The Color of Objects
The color of a transparent or translucent object is the color of the light it transmits.
Light - Light and Color
Combining Colors
As pigments are added together, fewer colors of light are reflected and more are absorbed.
Light
Building VocabularyUsing a word in a sentence helps you think about how best to explain the word. After you read the section, carefully note the definition of each Key Term. Also note other details in the paragraph that contain the definition. Use all this information to write a sentence for each Key Term.
- Light and Color
Key Terms: Examples:
transparent material A transparent material transmits most of the light that strikes it.
translucent material A translucent material scatters light as it passes through.
opaque material An opaque material reflects or absorbs all of the light that strikes it.
Key Terms: Examples:
primary colors
secondary color
complementary colors
pigment
Three colors that can combine to make any other color are called primary colors.
Two primary colors combine in equal amounts to produce a secondary color.
Any two colors that combine to form white light are called complementary colors.
Pigments are colored substances that are used to color other materials.
Light
Color
Click the Video button to watch a movie about color.
- Light and Color
Light
Links on Colors
Click the SciLinks button for links on colors.
- Light and Color
Light
End of Section:Light and Color
Light - Reflection and Mirrors
Reflection of Light Rays
The two ways in which a surface can reflect light are regular reflection and diffuse reflection.
Light - Reflection and Mirrors
Concave Mirrors
A mirror with a surface that curves inward like the inside of a bowl is a concave mirror.
Light - Reflection and Mirrors
Concave Mirrors
Ray diagrams show where an image forms and the size of the image. The steps below show how to draw a ray diagram.
Light - Reflection and Mirrors
Concave Mirrors
Concave mirrors can form either virtual images or real images.
Light - Reflection and Mirrors
Convex Mirrors
A mirror with a surface that curves outward is called a convex mirror.
Light
Mirrors Activity
Click the Active Art button to open a browser window and access Active Art about mirrors.
- Reflection and Mirrors
Light
Comparing and ContrastingAs you read, compare and contrast concave and convex mirrors in a Venn diagram like the one below. Write the similarities in the space where the circles overlap and the differences on the left and right sides.
Concave Mirror Convex Mirror
Real images
Virtual images
Curves outwardEnlarged
images
Curves inward
Reduced images
- Reflection and Mirrors
Light
End of Section:Reflection and
Mirrors
Light
Bending Light
The index of refraction of a medium is a measure of how much light bends as it travels from air into the medium. The table shows the index of refraction of some common mediums.
- Refraction and Lenses
Light
Bending Light
Diamond causes the greatest change in the direction of a light ray traveling from air.
Interpreting Data:
Which medium causes the greatest change in the direction of a light ray?
- Refraction and Lenses
Light
Bending Light
According to the graph, most solids bend light more than liquids do (quartz is an exception).
Interpreting Data:
According to the table, which tends to bend light more: solids or liquids?
- Refraction and Lenses
Light
Bending Light
You would not expect light to bend if it entered corn oil at an angle after traveling through glycerol, because corn oil and glycerol have the same value for the index of refraction.
Predicting:
Would you expect light to bend if it entered corn oil at an angle after traveling through glycerol? Explain.
- Refraction and Lenses
Light - Refraction and Lenses
Refraction of Light
When light rays enter a medium at an angle, the change in speed causes the rays to bend or change direction.
Light - Refraction and Lenses
Lenses
A lens is a curved piece of glass or other transparent material.
Light - Refraction and Lenses
Lenses
An object’s position relative to the focal point determines whether a convex lens forms a real image or a virtual image.
Light - Refraction and Lenses
Lenses
A concave lens can produce only virtual images because parallel light rays passing through the lens never meet.
Light
Lenses Activity
Click the Active Art button to open a browser window and access Active Art about lenses.
- Refraction and Lenses
Light
Asking QuestionsBefore you read, preview the red headings. In a graphic organizer like the one below, ask a what, when, where, or how question for each heading. As you read, write answers to your questions.
When does refraction occur?
When light rays enter a medium at an angle
What are the types of lenses?
Concave and convex lenses
Question Answer
- Refraction and Lenses
Light
End of Section:Refraction and
Lenses
Light - Seeing Light
Correcting Vision
Concave lenses are used to correct nearsightedness. Convex lenses are used to correct farsightedness.
Light
SequencingSequence is the order in which the steps in a process occur. As you read, make a flowchart that shows how you see objects. Put the steps of the process in separate boxes in the order in which they occur.
How You See Objects
Light enters the eye.
Light focuses on the retina.
An image forms.
Rods and cones send signals to the brain.
- Seeing Light
Light
More on Eyesight
Click the PHSchool.com button for an activity about eyesight.
- Seeing Light
Light
End of Section:Seeing Light
Light - Using Light
Optical Instruments
A telescope forms enlarged images of distant objects. Telescopes use lenses or mirrors to collect and focus light from distant objects.
Light - Using Light
Optical Instruments
A microscope uses a combination of lenses to produce and magnify an image.
Light - Using Light
Optical Instruments
The lens of the camera focuses light to form a real, upside-down image on film in the back of the camera.
Light - Using Light
Lasers
Laser light consists of light waves that all have the same wavelength, or color. The waves are coherent, or in step.
Light - Using Light
Optical Fibers
The floodlight in the swimming pool gives off light rays that travel to the surface. If the angle of incidence is great enough, a light ray is completely reflected back into the water. This complete reflection of light by the inside surface of a medium is called total internal reflection.
Light - Using Light
Optical Fibers
Optical fibers can carry a laser beam for long distances because the beam stays totally inside the fiber as it travels.
Light
Building Vocabulary
- Using Light
Key Terms: Examples:
telescope A telescope is a device that uses lenses or mirrors to collect and focus light from distant objects.
refracting telescope A refracting telescope is a telescope that uses convex lenses to focus light.
objective An objective is the large lens in a telescope or microscope that gathers and focuses light.
eyepiece An eyepiece is the lens near the eye in a telescope or microscope that magnifies the image.
reflecting telescope A reflecting telescope is a telescope that uses a concave mirror to gather light.
Key Terms: Examples:
microscope
camera
laser
hologram
optical fiber
A microscope is an instrument that forms enlarged images of tiny objects using lenses.
A camera is a device that uses lenses to focus light on film to record an image.
A laser is a device that produces an intense beam of coherent light.
A hologram is a three-dimensional photograph created by a laser.
An optical fiber is a strand of glass or plastic that can carry light long distances.
Key Terms: Examples:
total internal reflection The total internal reflection is the complete reflection of light by the inside surface of a medium.
A definition states the meaning of a word or phrase by telling about its most important feature or function. Carefully read the definition of each Key Term. Then write a definition of each Key Term in your own words.
Light
Links on Lasers
Click the SciLinks button for links on lasers.
- Using Light
Light
End of Section:Using Light
Light
Graphic Organizer
Virtual
Type of Mirror Effect on Light Rays Type of Image
Type of lens Effect on Light Rays Type of Image
Plane Regular reflection
Real or virtual
Convex Spread out
Convex
Virtual
Concave Converge
Virtual
Converge Real or virtual
Concave Spread out
Light
End of Section:Graphic Organizer
