Glass prism and its refractive index

In summary, the conversation discusses the angles and calculations involved in finding the refractive index of a prism. The prism is an equilateral triangle with angles of 60°. Using Snell's law, the refractive index is found to be 1.628, which is plausible for glass. For the second part, the symmetry principle is used to find the refractive index.
  • #1
orangephysik
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Homework Statement
A prism made from glass with a refractive index of n has the form of an equilateral triangle. A light ray is directed to one side of the prism with has an angle of α = 24.5° to the ground. You observe that the light ray inside the prism travels parallel to the ground.

a) Calculate the refractive index n.
b) Find the angle at which the ray leaves the prism and find β.
Relevant Equations
Snell's law: n_1*sin(m) = n_2 * sin(n)
All angles inside of a triangle sum up to 180°
Properties of equilateral triangles and isosceles triangles
Hi, I've attached the photo of the diagram, a photo of my drawings on the diagram.

for a): Since the prism is an equalateral triangle, all angles inside the prism is 60°. This means the angle adjacent to α is 180° - 60° = 120°, which means the last angle is 180° - 24.5° - 120° = 35.5°. The smaller triangle within the prism is an isosceles triangle, and by intuition the angle in the middle is 120° and the two angles on the sides are 30°.

Now with snell's law, n_vacuum * sin(γ_1) = n * sin(30°) and γ_1 = 90° - 35.5° 54.5°.
Plugging these values in, I got n = 1.628.

Is this correct? I thought the solution is plausible since the refractive index of a glass is usually around 1.5.

and for b) I just used the equation from snell's law again, n * sin(30°) = n_vacuum * sin(γ_2).
 

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  • #2
It looks correct to me=a google shows flint glass can have n=1.63. Perhaps that is what they use for the prism.
For part (b), you can simply apply symmetry principles.
 
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FAQ: Glass prism and its refractive index

What is a glass prism?

A glass prism is a transparent optical element with flat, polished surfaces that refract light. At least two of the flat surfaces must have an angle between them. The most common shape is a triangular prism, which is used to disperse light into its constituent spectral colors.

How does a glass prism refract light?

A glass prism refracts light due to the change in speed of light as it passes from one medium (air) into another medium (glass). This change in speed causes the light to bend at the interface between the two media. The amount of bending depends on the angle of incidence and the refractive index of the glass.

What is the refractive index of a glass prism?

The refractive index of a glass prism is a measure of how much the prism can bend light. It is defined as the ratio of the speed of light in a vacuum to the speed of light in the glass. For typical types of glass used in prisms, the refractive index ranges from about 1.5 to 1.9.

Why does a glass prism disperse light into a spectrum?

A glass prism disperses light into a spectrum because different wavelengths of light are refracted by different amounts. Shorter wavelengths (blue light) are refracted more than longer wavelengths (red light). This separation of light into its constituent colors is known as dispersion.

How is the refractive index of a glass prism measured?

The refractive index of a glass prism can be measured using various methods, such as the minimum deviation method or by using a refractometer. In the minimum deviation method, a monochromatic light beam is passed through the prism, and the angle of minimum deviation is measured. This angle, along with the geometry of the prism, is used to calculate the refractive index.

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