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Refraction Textbook: p. 334 - 335

Refraction Textbook: p. 334 - 335. “Bent” Spoons and Straws!. Water Droplets. Rainbows. Sundogs!. A Squished Sun?. Slow down, looks wet ahead!. So thirsty. Uh, is this possible?. Is the shark really where you think it is?. Refraction.

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Refraction Textbook: p. 334 - 335

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  1. RefractionTextbook: p. 334 - 335

  2. “Bent” Spoons and Straws!

  3. Water Droplets

  4. Rainbows

  5. Sundogs!

  6. A Squished Sun?

  7. Slow down, looks wet ahead!

  8. So thirsty........

  9. Uh, is this possible?

  10. Is the shark really where you think it is?

  11. Refraction When you added water to the cup and the coin “appeared” you experienced refraction. The light from the coin changed direction as it went from water into air, and then into your eyes. Refraction Is the bending or change in direction of light when it travels from one substance into another. Refraction is also the basis for how lenses work.

  12. What is the fastest thing in the universe? THE SPEED OF LIGHT = 300,000,000 m/s in space However.....the Speed of Light in water= 226,000,000 m/sor about 25% slower

  13. Light will travel at different speeds through different materials. • Examples • Space or Air: 300,000,000 m/s • Water: 226,000,000 m/s • Glass: 197,000,000 m/s • Sapphire 170,000,000 m/s • Diamond 125,000,000 m/s

  14. Light slows down when it leaves space or air and enters any other substance. • Light speeds up when it leaves a substance and enters space or air

  15. But why does the light bend? • The speed of light changes when it moves from one substance into another (ex. From air into water). The line between the two substances is called the boundary. - ANALOGIES: a wagon travelling from pavement on to sand. - soldiers marching from roadway to a muddy field

  16. Another analogy: a car travelling from smooth pavement to mud or vice versa.

  17. Or imagine you are a lifeguard on a beach and need to rescue someone. To reach the person most quickly, you would run along the beach first and enter the water only when you had to.

  18. In the same way, light bends when it reaches a substance that causes it to slow down or speed up

  19. The Rules of Refraction Angle of Refraction = the angle between the refracted ray & the normal. 1. If the light moves from a faster substance to a slower substance, the light will bend towards the normal. 2. If the light moves from a slower substance to a faster substance, the light will bend away from the normal.

  20. Refraction Question #1 Where is the normal? Air Air What path will light take when it passes through the chamber?

  21. Refraction Question #2 What path will the ray take? Air Water Why is the path bent toward the normal? - Because water slows down the light.

  22. Refraction Question #3 What path will the ray take? Water Air Why is the path bent away from the normal? - Because air speeds the light up.

  23. Dispersion • White light - 7 different colours (ROYGBIV) have different wavelengths (red the longest, violet the shortest). • Therefore - each colour slows down to a greater extent when refracted • The angle of refraction will also differ. • Shorter wavelengths like VIOLET refract (bend) more than longer wavelengths. This is why the order of colours in a rainbow is always the same.

  24. Partial Reflection & Refraction What do a fish pond, an office building, and a pair of sunglasses have in common? - When light strikes these objects some of it is reflected, but a great deal is refracted at the same time.

  25. Partial Reflection and Refraction • Sometimes you can see through a window to the other side as well as a reflection of yourself or an object on ‘your’ side. • When light moves from one substance to another, some light reflects, some light refracts

  26. Why can you not see beneath the surface of the water? Because the angle of incidence is great, most of the sunlight is being reflected from the water’s surface.

  27. Why can you see beneath the surface closer to you? Because the angle of incidence is small (the sun is overhead), most of its rays are refracted into the water and little is reflected.

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