14.1 Bending of light

Determining the refractive index of glass

In an experiment, a ray of light is directed towards a semi-circular glass block at various angles of incidence. The following table shows the results obtained.

Example 1

i

r

air

glass

normal

Angle of incidence i 0 15 30 45 60 75Angle of refraction r 0 9 18 26 33 40

14.1 Bending of light

(a) Plot a graph of sin i against sin r. How are sin i and sin r related?

sin isin r

0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5 0.55 0.6 0.65

0.2

0.4

0.6

0.8

1

sin i

sin r

(a) 00

0.2590.156

0.5000.309

0.7070.438

0.8660.545

0.9660.643

14.1 Bending of light

(b) From the graph in (a), find the refractive index of the glass.

(b)

1.55

As the graph is a straight line that passes through the origin, sin i is directly proportional to sin r.

slope of the graphrefractive index of the glass

058.009.0