# The light rays travelling from rarer to denser medium is given in the figure 1. Redraw the diagram and correct it

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The light rays travelling from rarer to denser medium is given in the figure

1. Redraw the diagram and correct it

2. State the law relating i and r for retracted ray.

3. Velocity of light in water is 2.25 × 108 m/s, If angle of incidence is 30° calculate angle of refraction.

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1.

2. Snells law:

The ratio of the sine of the angle of incidence to the sine of the angle of refraction is a constant for a given pair of media and for the given colour of light used. This constant is known as the refractive index of second medium w.r. t. the first medium.

Explanation:

If ‘i’ is the angle of incidence in the first medium and ‘r’ is the angle of refraction in the second medium, then by Snell’s law,

$\frac{sin\,i}{sin\,r}=\frac{n_2}{n_1}$ = 1n2 = a constant

Where 1n2 is the refractive index of the second medium with respect to the first medium. If the first medium is air, then sin i/sin r is known as absolute refractive index of the second medium.

i.e, $\frac{sin\,i}{sin\,r}$ = n

where ‘n’ is the refractive index of the second medium.

3.  n = $\frac{sin\,i}{sin\,r}$ But n = $\frac{c}{v}$

$\frac{c}{v}$ = $\frac{sin\,i}{sin\,r}$

$\frac{3\times10^8}{2.25\times10^8}$ = $\frac{sin\,30°}{sin\,r}$

sin r = $\frac{\frac{1}{2}\times 2.25\times10^8}{2.25\times10^8}$

sin r = 0.375, r = 22°