Guiding Question How does light behave at the boundary between two different materials? 1
Key Vocabulary Key Vocabulary } angle of incidence } angle of refraction } critical angle } function } refraction } pattern } structure } total internal reflection } transmission, transmit 2
Get Started What are some characteristics of light? } Record your ideas in your notebook. 3
Get Started Refraction } A phenomenon that occurs when a wave encounters a boundary between two materials through which the wave can pass. 4
Introduction Read the introduction and look for key ideas 5
Do the Activity Complete procedure part A: Refraction } Record your data in your notebook. 6
Do the Activity Light ray diagram for refraction 7
Do the Activity What do you think happens when you keep increasing the angle of the incident ray in a more dense medium? } Share your thoughts with the class. 8
Do the Activity Complete procedure part B: Total Internal Reflection } Record your data in your notebook. 9
Do the Activity How did the evidence you collected in this activity lead you to a conclusion about how light waves behave? } Share your thoughts with the class. 10
Build Understanding Teacher demonstration } Refraction and total internal reflection using a laser pointer 11
Analysis Analysis 1 } Draw a diagram with labels that shows how the light traveled through the milky water when it was a. directed down the normal line. b. directed at an angle. Look at teacher book page 105 12
Analysis Analysis 2 } Look at the data below that show the refraction of light from one medium to another for various materials. The incident angle is the same for all the materials. 13
Analysis Analysis 2 continued } Your friend looks at these data and says, I see a general trend showing that as the optical density of a material increases, the critical angle also increases. Do you agree or disagree with your friend? Explain your conclusion using evidence from the table. I disagree with the statement.the data show that as optical density increases, the critical angle decreases.there is an inverse relationship between the optical density and the critical angle, not a direct relationship. A more optically dense material will refract light more, leading to a smaller critical angle. A less optically dense material will not result in as much refraction, leading to a larger critical angle. 14
Analysis Analysis 3 } The principle of total internal reflection is used in fiber optic technology. A wave signal is sent down a glass tube at greater than the critical angle so that it is reflected off the interior of the tube as it travels. Refer to teacher book page 106 15
Analysis Analysis 3 continued } Copy the close-up diagram of a fiber optic cable below. Draw arrow(s) that show a possible ray that is totally internally reflected through the tube. 16
Analysis Analysis 4 } The functioning of the human eyeball depends on the refraction of light. When light comes into the eye, first the cornea and then the lens refracts the light so that it focuses on the retina. The lens is flexible and is controlled by muscles in the eye. The curvature of the lens changes in order to focus objects at different distances. If the lens does not refract properly, the light rays do not come together at a point on the retina. 17
Analysis Analysis 4 continued } When the light focuses past the retina, the person will have blurry vision at close distances. This person would be considered farsighted. Farsightedness can be corrected with eyeglasses or contact lenses that refract the light inwards before it enters the eye. 18
Analysis Analysis 4 continued } The opposite problem, or nearsightedness, occurs when the light entering the eye comes to a point before it hits the retina. It results in blurry vision at farther distances. This is corrected by refracting the light outwards before it enters the eye. 19
Analysis Analysis 4 continued } Which one of the following eyeglass lenses can be used to make the light fall on the retina of a nearsighted person, as shown below? Draw a diagram that shows the lens, the eye, and two rays of light converging on the retina. See Teacher Book for Diagram pg 107 20
Revisit the Guiding Question How does light behave at the boundary between two different materials? 21
Review Key Vocabulary definitions } angle of incidence - The angle between the incoming light ray and the normal line when light hits the surface of a different medium. } angle of refraction - The angle between the normal line and the path the light travels in the new medium when light is transmitted from one medium to another. 22
Review Key Vocabulary definitions } critical angle - The angle of incidence in a more dense medium that produces a 90-degree angle of refraction in a less dense medium. } function - A purpose or function which a particular thing can perform. } refraction - The redirection of light at the boundary between two transparent materials. 23
Review Key Vocabulary definitions } pattern - Something that happens in a repeated and predictable way. } structure - The way something is formed, built, or organized. } total internal reflection - The reflection of light that occurs when the angle of incidence is greater than the critical angle for a pair of media. 24
Review Key Vocabulary definitions } transmission - The act of energy passing through a medium or vacuum. 25