4-5.3 Summarize how light travels and explain what happens when it strikes an object (including reflection, refraction, and absorption).
The Behavior of Light
Essential Question: Using the three states of matter, how can light be reflected, absorbed, and refracted?
How Light Travels
Light travels in a straight line until it hits something. You can draw light as an arrow or line to show its path and direction. The diagram below shows three things that can happen when light strikes an object.
Essential Question: Using the three states of matter, how can light be reflected, absorbed, and refracted?
How Light Travels
Light travels in a straight line until it hits something. You can draw light as an arrow or line to show its path and direction. The diagram below shows three things that can happen when light strikes an object.
Reflection
Reflection is the bouncing of light off a surface. When you look in a mirror, the mirror reflects light into your eyes. The surface of a lake also reflects light into your eyes. So do the pages of your notebook. Any solid or liquid surface can reflect light. That is why you can see the surface. You can see yourself in a mirror or calm lake because they have very smooth surfaces. Rougher surfaces, like this page, scatter light. They cause it to bounce off in all directions. |
Absorption
Some light is always absorbed, or taken in, when it strikes a surface. What happens to light that is absorbed? Your skin absorbs sunlight. As your skin does this, you feel it getting warmer. Remember that light is a form of energy. In your skin, light changes to a different form of energy. That form of energy is heat. Absorption is the process by which materials take in light and change it into heat. Objects with dark surfaces absorb more light than objects with lighter surfaces. On a sunny day, you will feel warmer in a black T-shirt than in a white T-shirt. A black shirt absorbs most of the light that strikes it. A white shirt reflects most of this light. When light is absorbed it does not pass through or reflect from a material. It remains in the material as another form of energy. The color of objects are determined by the light that is not absorbed but is reflected by the objects. The color orange is not being absorbed in a carrot. All other colors of light striking the carrot are absorbed (R, Y, G, B, I, V). A red object is red, because, it absorbs all rays of light except the red ones that are reflected. Different materials absorb more light of certain colors and reflect more light of other colors. An object that looks black absorbs most colors of light. An object that looks white reflects most colors of light. |
Refraction
Some materials transmit light, or let light pass through them. Empty space also transmits light. Glass, water, and air are materials that transmit light. Light changes direction when it passes from one of these materials into another. This process is called refraction. You can think of refraction as the bending of light. If you put a pencil in a glass of water, the pencil looks bent or broken. That is because light is refracted as it passes from air into water. The refraction (bending) of light as it passes from air into water causes an optical illusion: objects in the water appear broken or bent at the water’s surface. Refraction Light travels in straight lines, but it can be refracted, or bent. Refraction occurs only when the light rays enter or leave a substance at an angle. If the rays are straight up and down, they do not bend. |
Learning Task #1:
Discovery Ed Techbooks: - Reflection " What happens when light hits a surface?" ●Have students demonstrate the reflection of light using a flashlight and mirror. List other items that would reflect light (smooth and shiny) on class chart. Learning Task #2: ● Have students demonstrate the absorption of light using a flashlight and different colored items. (A red item would reflect red and absorb the other colors of light). Learning Task #3: Discovery Ed TechBooks: - Refraction "What happens when light passes through a transparent material?" ● Have students demonstrate the refraction of light using a flashlight and a prism. Also, have them place a straw/ pencil in a clear cup of water, and observe what happens as the light bends. Learning Task #4: Read Works Article: ● Light Bounces |
Resources:
Techbook Resources: ● Refracted Light Video Segment ABDO e-Book: ● Light in the Real World - pgs. 19-23 Read Works Article: ● Light Bounces Discovery Ed Techbooks: ● Reflection ● Refraction DE Articles: ● A Native American Legend ● Gone Fishing DE Interactives: ● Reflect Animation ● Reflection Exploration ● Refraction Action Exploration ● Refraction Exploration |