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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. (1) How long does it take for a short pulse of light to travel from one end of the glass to the other?

Respuesta :

Answer:

[tex] t = \frac{10n}{f}= \frac{10*1.5}{f}= \frac{15}{f}[/tex]

Explanation:

For this case we know that the light without any obstruction and in the free space travels with a speed of [tex] c = 3x10^8 \frac{m}{s}[/tex]

When we have a surface like a glass we know that the velocity is given by the following expression:

[tex] v = \frac{c}{n}[/tex]

Where n is the refraction index, and on this case is given n = 1.5

For this case we know that the lenght of the glass is L and the wavalength is also given [tex] \lambda = \frac{L}{10}[/tex]

We know the following relation between distance and time:

[tex] D = Vt[/tex]

And if we solve for t we got:

[tex] t= \frac{D}{v}[/tex]

For this case the value of D = L and v =c/n and if we replace we got:

[tex] t = \frac{D}{v}= \frac{L}{\frac{c}{n}}= \frac{nL}{c}[/tex]  (1)

Now we need to found a way to incorporate the wavelength into this formula and we have the following expression:

[tex] c = \lambda f[/tex]

If we replace this condition into equation (1) we got:

[tex] t = \frac{nL}{\lambda f}[/tex]

And we can use the condition that [tex] \lambda = \frac{L}{10}[/tex] and we have this:

[tex] t = \frac{nL}{\frac{L}{10} f}[/tex]

We can cancel the L terms and we have just:

[tex] t = \frac{10n}{f}= \frac{10*1.5}{f}= \frac{15}{f}[/tex]

And that would be the time that it takes a short pulse of light to travel from one end of the glass to the other.

It will take "[tex]t = \frac{15}{f}[/tex]". A further explanation is below.

Given:

Index of refraction,

  • n = 15

Wavelength,

  • λ = [tex]\frac{L}{10}[/tex]

As we know,

→ [tex]t = \frac{d}{v}[/tex]

  [tex]t = \frac{L}{\frac{c}{n} } = n\times \frac{L}{c}[/tex]

here, [tex]c = \lambda\times f[/tex]

then,

→ [tex]t = n\times \frac{L}{c} = n\times \frac{L}{\lambda\times f}[/tex]

By substituting the values, we get

     [tex]= n\times \frac{L}{\lambda\times f}[/tex]

     [tex]= 10\times \frac{n}{f}[/tex]

   [tex]t = \frac{15}{f}[/tex]

Thus the above answer is correct.

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