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Refraction. Refraction. Refraction – change in direction of light as it passes at an angle from one medium into another (examples of medium – air, water, glass etc ). Why?. We know the speed of light in a vacuum is 3.00 x 10 8 m/s. It is actually 2.997 924 x 10 8 m/s.
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Refraction • Refraction – change in direction of light as it passes at an angle from one medium into another (examples of medium – air, water, glass etc)
Why? • We know the speed of light in a vacuum is 3.00 x 108 m/s. • It is actually 2.997 924 x 108 m/s. • In air, the speed of light is reduced by 0.000 87 x 108 m/s. • In water, the speed of light is about ¾ the speed it travels in a vacuum. • The speed of light depends on the medium it travels through. • The more optically dense a medium is, the slower the light passes through it.
As light (or any wave) changes speed, it changes direction…unless it hits the new medium straight on at a perfect angle of 90.
Rules • Light bends TOWARDS to normal when the speed is slowed • Light bends AWAY from normal when the speed is sped up
incident ray MEDIUM #1 MEDIUM #2
Sample Question • If I had a beam of light passing from a water medium to an acrylic medium, would the light bend towards or away from the normal?
Angle of Refraction • The difference between the refracted ray and the normal
Partial Reflection and Refraction • Some light that hits a surface refracts into the new medium • Some of the light is reflected back into the same medium • Ex. two way mirrors and mirrored sunglasses
Homework • Pg 519 #1-4