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Refraction and the Refractive Index

Refraction and the Refractive Index. Why does light bend when it goes from one substance into another ?. Refractive Index. Because different substances have different Refractive Indices !. So what’s that ?.

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Refraction and the Refractive Index

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  1. Refraction and the Refractive Index • Why does light bend when it goes from one substance into another ?

  2. Refractive Index • Because different substances have different Refractive Indices !

  3. So what’s that ? • Light travels at different speeds through different substances. • The property of a substance which causes this is called the REFRACTIVE INDEX

  4. It is a Number • Refractive index is a number. • It is the ratio of the speed of light in a vacuum to its speed in a substance • By convention, we give it the symbol “n”. C = n.V

  5. What about the Bending ? • Light will bend at the junction of two different substances because of the Principle of Least Time.

  6. Fermat Thought of It back around 1650 • Pierre de Fermat was a French mathematician. • Fermat’s principle of least time states that: • Light will travel in whatever direction will minimise the time taken to complete its journey.

  7. ......and this means • The shortest journey for light passing through several different substances is Never a straight line.

  8. Snell’s Law • This gives rise to Snell’s Law • n1.sinA = n2.sinB

  9. It also Explains...... • Why the sky is blue • How rainbows happen • Why lenses work • ........and many other phenomena

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