REFRACTION PRODUCED BY A PARALLEL SIDED SLAB

 

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When a ray of light travels from one medium to a second medium, refraction occurs at both the interface at point ‘B’ and then once again refraction take place at point ‘C’ from lower interface.

By Snell’s law,

\frac{{\sin \,{i_1}}}{{\sin \,{r_1}}}\, = \,{n_{ga}}\,\,(at point ‘B’)         ………………….(1)

and \frac{{\sin \,{i_2}}}{{\sin \,{r_2}}}\, = \,{n_{ag}}\,\,(at point ‘C’)

Or \frac{{\sin \,{r_2}}}{{\sin \,{i_2}}}\, = \,{n_{ga}}\,\,                        ………………….. (2)

From (1) and (2)

\frac{{\sin \,{i_1}}}{{\sin \,{r_1}}}\, = \,\frac{{\sin \,{r_2}}}{{\sin \,{i_2}}}\, …………………… (3)

Here {r_1}\, = \,{i_2}(alternate interior angle)

Substituting in equation (3) we have:

\sin \,{i_1}\, = \,\sin \,{r_2}

Or {i_1}\, = \,{r_2}

Thus the emergent ray is parallel to the incident ray.

Post Author: E-Physics

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