Question

1. Briefly explain the following optical classification of materials:                  [3]

-Transparent materials

-Translucent materials

- Opaque materials

1. A light beam in air hits a sheet of crown glass. Compute the velocity of light in crown glass.
2. (n_air = 1.0003, n_{crown glass} = 1.52, c = 3 × 10⁸m/s).        

Answer 1

TRANSPARENT -:

these are the materials which allows light to pass through them completely. and hence, we can see clearly through transparent objects.

TRANSLUCENT :-

these are the materials which allows light to pass through them but not completely. half of the light get absorbed. that's why we can't see through it clearly.

OPAQUE: -

these are the materials which don't allow light to pass through them. almost all light get absorbed. that's why we can't see through opaque objects.

For example

transparent - glass window

translucent - oily paper, frosted glass, glass used in bathroom.

opaque - wood, notebook, metal sheet.

$v=\frac{c}{n}$

$v_{air}=\frac{3\times10^{8}}{1.0003}=2.99\times10^{8}m/sec$

$$v_{glass}=\frac{3\times10^8}{1.52}=1.97\times10^8m/sec$$

$v_{air}>v_{glass}$