Topic explanation

Standard explanation

n = speed in vacuum (or air) / speed in the medium. Air is about 1, water about 1.33, glass about 1.5. Larger n means slower light in that medium.

Key points

• c / v
• larger n -> slower
• change of speed
• towards the normal if slower
• Refraction And Snell'S Law: Refraction is the change of speed (and usually direction) when light enters a new medium. In glass o
• Refractive Index N: n = speed in vacuum (or air) / speed in the medium. Air is about 1, water about 1.33, glass about 1.
• Snell'S Law: n1 sin i = n2 sin r, with i and r from the normal. From air into glass: sin i / sin r = n_glass. Fre
• REFRACTIVE INDEX n: n = speed in vacuum (or air) / speed in the medium. Air is about 1, water about 1.33, glass about 1.

Labelled diagram