# Calculating Wavelength of Light in Glass Slab

• sghaussi
In summary: I RIGHT THAT THE THICKNESS DOESN'T MATTER AS LONG AS YOU KEEP THE WAVEWIDTH THE SAME, EVEN IF THE THICKNESS OF THE MEDIUM CHANGES?Yes, the thickness of the medium doesn't matter as long as you keep the wave-width the same.
sghaussi
Hi! I was wondering if you can give me some adivice on how to approach this problem:

In a physics lab, light with a wavelength of 560 nm travels in air from a laser to a photocell in a time of 16.5 ns. When a slab of glass with a thickness of 0.860 m is placed in the light beam, with the beam incident along the normal to the parallel faces of the slab, it takes the light a time of 21.3 ns to travel from the laser to the photocell.

What is the wavelength of the light in the glass?
Use 3×108 m/s for the speed of light in a vacuum.

My main problem is that I don't know how the thickness of the medium is important.

Thank you in advance,
Sahar

how long did the light take to travel the glass?
thats when the thickness counts
you can get your index once you figure this out
as the light goes through the glass, the frequency doesn't change just the wavelength
what does this tell you?

Last edited:
sghaussi said:
Hi! I was wondering if you can give me some adivice on how to approach this problem:

In a physics lab, light with a wavelength of 560 nm travels in air from a laser to a photocell in a time of 16.5 ns. When a slab of glass with a thickness of 0.860 m is placed in the light beam, with the beam incident along the normal to the parallel faces of the slab, it takes the light a time of 21.3 ns to travel from the laser to the photocell.

What is the wavelength of the light in the glass?
Use 3×108 m/s for the speed of light in a vacuum.

My main problem is that I don't know how the thickness of the medium is important.
The first thing to do is to find how long the original path is.

$$s_0 = c\Delta t_0$$

For the path through the glass, there are two parts:

$$s_{air} = c\Delta t_{air}$$ and

$$s_{glass} = v_{glass}\Delta t_{glass}$$

so you know, or can work out: $s_{air},\Delta t_{air}, s_{glass}, \Delta t_{glass}$

From that you should be able to work out $v_{glass}$ and wavelength follows from that.

AM

Last edited:

## 1. How do you calculate the wavelength of light in a glass slab?

To calculate the wavelength of light in a glass slab, you can use the formula λ = λ0/n, where λ is the wavelength in the glass, λ0 is the wavelength in air or vacuum, and n is the refractive index of the glass slab.

## 2. What is the refractive index of a glass slab?

The refractive index of a glass slab is a measure of how much the speed of light is reduced when it passes through the glass. It is typically denoted by the symbol n and can range from around 1.3 to 1.9, depending on the type of glass used.

## 3. How does the thickness of the glass slab affect the wavelength of light?

The thickness of the glass slab does not affect the wavelength of light in the glass. The wavelength is solely determined by the refractive index of the glass and the wavelength in air or vacuum.

## 4. Can the wavelength of light in a glass slab be longer than the wavelength in air or vacuum?

No, the wavelength of light in a glass slab cannot be longer than the wavelength in air or vacuum. The refractive index of the glass always causes the wavelength to be shorter in the glass compared to in air or vacuum.

## 5. How does the color of light affect the wavelength in a glass slab?

The color of light does not directly affect the wavelength in a glass slab. However, different colors of light have different wavelengths in air or vacuum, which in turn will result in different wavelengths in the glass based on the refractive index.

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