Refraction of Light

Learning Objective: Describe what happens to light when it goes from air to another substance. Study the relationship between the angle of incidence, the angle of refraction, and relate them to the index of refraction to understand Snell’s law. Success Criteria Observe refraction Measure angles of incidence and refraction Measure the critical angle Observe total internal reflection Do Now: Copy LO and SC on new left side page WDYS/WDYT pg. 558 Agenda: Do Now Investigate Summary

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Learning Objective: Describe what happens to light when it goes from air to another substance. Study the relationship between the angle of incidence, the angle of refraction, and relate them to the index of refraction to understand Snell’s law. Success Criteria Observe refraction Measure angles of incidence and refraction Measure the critical angle Observe total internal reflection Do Now: Explain how this toy works Agenda: Do Now Physics Talk Summary

What is refraction? What materials can cause refraction? How much will light bend? The bending of light as it travels from one medium to another Acrylic, glass, water, diamonds Depends on the properties of the two materials

What is the Index of Refraction? A property of the materials at an interface (?) that determind the relationship between the angle of incidence and the angle of refraction Objects with high index of refraction (diamond) bend light a lot Objects with a low index of refraction (glass bend light a little)

How much will light bend? If the neighboring materials have an index of refraction that is similar, light will bend very little air  glass  air Little bending because index of refraction is similar Air  diamond  air Lots of bending because index of refraction is very different

What is the Law of Reflection, also known as Snell’s Law? The relationship between the index of refraction and the ratio of the sine of angle of incidence to the sine of angle of refraction at the boundary of the two media where the refraction takes place. Huh? Put this in your own words!

More on Snell’s Law When light enters a substance from low index of refraction to high index of refraction, the light bends toward the normal. When light leaves a substance with high index of refraction to low index of refraction, the light bends away from the normal Larger difference in index of refraction, the more refraction will occur

What is the critical angle?When the angle of refraction (low to high index of refraction) is 90° If the angle of refraction is greater than 90°, the light will reflect back into the substance as though it were a mirror. This is how laser light reflects down a glass or plastic tube.

What is total internal reflection? When the refracting medium acts like a perfect mirror and the reflected light stays inside the medium

Is there an equation for the index of refraction?

What does it mean? How do you know? Why should you care? Learning Objective and Success Criteria Reflections

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