Question

A beam of light from a monochromatic laser shines into a piece of glass. The glass has thickness L and index of refraction n=1.5. The wavelength of the laser light in vacuum is L/10 and its frequency is f. In this problem, neither the constant c nor its numerical value should appear in any of your answers. How long does it take for a short pulse of light to travel from one end of the glass to the other? Express your answer in terms of the frequency, f. Use the numeric value given for n in the introduction.

Answer 1

Answer:

Time taken = f/15

Explanation:

Detailed explanation and calculation is shown in the image below

Answer 2

Answer:

$t = \frac{15}{f}$

Explanation:

Light travels with the speed of light in a free space vacuum

In a piece of glass . the light travels at a speed $v = \frac{c}{n}$

where ;

n = index of refraction

The time $t = \frac{L}{v}$

where;

L = length of the glass slab

velocity $v = \frac{d}{t}$

$t= \frac{d}{v}$

$t = \frac{L}{\frac{c}{n}} \\\\t = \frac {n * L}{c}$

Also;  $c =\lambda f$

$t = \frac{n*L}{\lambda f}$

Given that;

wavelength $\lambda = L/10$; and n = 1.5;  we have:

$t = \frac{n*L}{\frac{L}{10} f}$

$t = \frac{10*n}{f}$

$t = \frac{10*1.5}{f}$

$t = \frac{15}{f}$