Refractionthe bending of a light ray as it

Refractionthe bending of a light ray as it passes from one medium to another air glass air light slows down (v<c)

Transparent • Light shines through; can clearly see through Translucent • Partially transparent Opaque • Rays of light can not pass through 2

The Refractive Index (n) is a measure of by how much light slows down in a medium. Note a. nair/ vaccuum = 1. 0 b. any medium n > 1 c. n has no units The speed of light in water is 2. 29 x 108 ms-1. What is the refraction index of water? Formula from wave Paper

Light slows down when it enters a high density material from a low density medium. This causes the light to bend. Partial reflection Refraction 1 Refraction 2

n 1 = initial medium n 2 = final medium 1 = incident angle 2 = refracted angle Don’t forget to measure angles from The Normal

Bends away from the normal Bends toward the normal

Snell’s Law n 1 sin 1 = n 2 sin 2 = angle to the normal (0) n = refractive index (no unit)

Notice: If n 2>n 1 : light ray bends toward the normal If n 2<n 1 : light ray bends away from the normal n 1 sin 1 = n 2 sin 2 Snell’s Law

Ex: air 60 water Find both the angle of reflection and the angle of refraction for this light ray incident upon water.

See 1 Snells law applet See 3 Snells law & TIR applet

Find nwater, nglass, ndiamond If V not know - find n using Snells law n 1 sin 1 = n 2 sin 2

A refractometer is a device that measures the refractive index of a liquid. This can be used to calculate the concentration of the liquid.

AIM: To find out the refractive index of a block of plastic and or glass using Snell’s Law.

Light Box activity

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Report expectations… Due Friday • Experimental data sheet • Can be shared with lab partner • Data table • Graph • On Grid paper • 2/3 size rule, labelled • Line of Best fit • Calculations • Show clearly how you determined nglass & nplastic • Questions answered 17