The Ray Model of Light Lesson 4. Light and Matter Light is represented as straight lines called...
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Transcript of The Ray Model of Light Lesson 4. Light and Matter Light is represented as straight lines called...
![Page 1: The Ray Model of Light Lesson 4. Light and Matter Light is represented as straight lines called rays, which show the direction that light travels. Ray.](https://reader036.fdocuments.in/reader036/viewer/2022062320/56649cef5503460f949bd370/html5/thumbnails/1.jpg)
The Ray Model of Light
Lesson 4
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Light and Matter• Light is represented as straight
lines called rays, which show the direction that light travels.
• Ray diagrams are drawings that show the path that light takes after it leaves its source. Each ray ends with an arrow to indicate the direction of travel.
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Light and Matter• Ray diagrams can help explain why
the brightness of a light changes with distance. The more rays that reach your eyes, the brighter the object appears
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Light and Matter• Ray diagrams are used to describe
what happens when light strikes an object.
• Light travels in straight lines until it strikes something.
• Materials have different properties which affects what happens when light strikes them
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Light and Matter• Transmit - Light passes through them.
Example: Clear glass
• Absorb – Light is absorbed by the object and turned into heat
• Reflect – Light bounces off the object.
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Light and MatterThe properties of materials can then be
further classified
• Transparent materials, such as clear glass or clear plastic, transmit light freely.
• Transparent materials absorb and reflect very little light. Example: a clear window
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Light and MatterTranslucent materials transmit some
light, but not enough to see through the material clearly. Example: A frosted window pane. Some light can pass through, but you cannot see what is on the other side of the frosted glass in any detail.
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Light and Matter• Opaque objects absorb and reflect
light, but they do not transmit it
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Shadows• A shadow occurs when an opaque
object blocks the direct light from a light source
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Shadows• Ray diagrams can be used to show
1.How the size of the shadow depends on the objects distance from the light source• A larger object will produce a larger
shadow• An object closer to the light source
will produce a larger shadow
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Shadows
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Shadows2. How the sharpness of the edges of a
shadow are depend on the objects distance from the light source and the size of the light source.
– The closer the object is to the light source the fuzzier the shadow is.
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Shadows• Large light sources provide shadows
with fuzzy edges - penumbra– This is due to the object only partially
blocking the light. • The umbra is the part of the shadow in which
all light rays from the light source are blocked
– Point source (Small light sources) show well defined shadows
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TShadows
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Drawing Light Ray Diagrams of Shadows
1. Draw a line from the top of the light source to the top of the opaque object and continue onto the wall
2. Draw a line from the top of the light source to the bottom of the opaque object and continue onto the wall
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Drawing Light Ray Diagrams of Shadows
3. Draw a line from the bottom of the light source to the top of the opaque object and continue onto the wall
4. Draw a line from the bottom of the light source to the bottom of the opaque object and continue onto the wall
5. Label the umbra and penumbra
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Examples
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Reflection of light• Even objects that do not reflect an
image still reflect light.
• Everything you can see in the room right now is reflecting light.
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Reflection of light• When light rays reflect off a rough
or uneven surface, they do not remain parallel but are scattered in different directions, resulting in a diffuse reflection. Because the light is scattered, the rooms lighting is even without bright spots.
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Questions – Hand in• 1. How does a transparent object interact with
light? K (1)• 2. How does a translucent object interact with
light? K (1)• 3. How does an opaque object interact with light?
K (1)• 4. What is diffuse reflection? C (1)• 5. Make two light ray shadow diagrams of your
choice. C (4)