Year 9 Science

Physics: Light – Refraction and Indices of Refraction

i) Law of Refraction (definition) = ______

______

ii) Another term for i) is SNELL’S LAW

Snell’s Law Equation: n1sinθ1 = n2sinθ2

n1 and n2 = indices of refraction

sinθ1 and sinθ2 = angles between light rays

Indices of Refraction of Some Materials

Material / n
Air / 1.00029
Ice / 1.31
Water / 1.33
Alcohol / 1.36
Oil / 1.48
Quartz / 1.46
Crown Glass / 1.52
Glycerol / 1.52
Ruby / 1.76
Diamond / 2.42

Refraction Problem Questions:

1. A ray of light enters a body of water at an angle of incidence of 30O. The refracted ray of light has an angle of refraction of 20O. Use a sharp pencil and ruler to draw a neat diagram to represent this situation.

2. A ray of light enters a thick plate of glass of index of refraction n = 1.52 at an angle of incidence of 45O. Use a sharp pencil and ruler to draw a neat diagram to represent this situation.

a) What is the angle of refraction of the ray at the upper surface of the glass?

b) When the ray reaches the lower surface of the glass it is refracted again and it emerges into air. What is the angle at which it emerges? Use a sharp pencil and ruler to draw a second neat diagram to represent this situation in addition to part a)

3. A ray of sunlight travels through the air (n = 1.00029) and approaches the surface of a smooth water pond (n = 1.33) at an angle of incidence of 40O. What is the angle of refraction?

4. A ray of light strikes a plate of window glass of index of refraction 1.5 with an angle of incidence of 50O.

a) What is the angle of refraction?

b) At what angle does the ray of light emerge on the other side of the glass?