27 Oct 2021

## Blog Post # Prism – Definition, Types of Prism, Unknown Facts, Examples, and More

## What is a Prism?

• When passing through a prism, the dispersion of light is the product of the white light wave being composed of various wavelengths.
• When entering the medium, they experience different speeds, a product that each color that forms has a different wavelength—white light.
• We will consider only monochromatic light for the present analysis, which will have a refractive index characteristic of the prism.
• We have a first interaction, where the incident ray is θ 1 is the incident angle, δ 1is the angle of refraction.
• Prisms come in many sizes and shapes that serve many functions. A significant group is called dispersive prisms.
• Then it will leave the prism after deviating from its original direction by an angle δ which we call angular deviation.

## Reflecting prisms

• In reflector prisms where scattering is not desirable, the light beam introduces so that at least one total internal reflection occurs to change the direction of propagation, the orientation of the image, or both.
• In the previous equations, when we have calculated the minimum dispersion, we realize that it is independent of the refractive index and the wavelength.
• The reflection will occur without any color preference, and the prism is called achromatic.
• The following show some of the many reflector prisms out there, which we can construct BSC-2 p C-1 glass.

## Different Types

### 1. Orthogonal prism

• This type of prism deflects the light at 90º.
• The rays perpendicular to the incident face. Note that the top and bottom of the image swap, that is, the arrow has flipped over without, however affecting the left and right sides.
• Consequently, it is an inverter system whose upper face acts as a flat mirror.

### 2. Porro Prism

• It is physically the same as the orthogonal prism, but we use it in a different orientation.
• After two internal reflections in a row, the beam deviate 180º. Therefore, it enters with the correct orientation.
• It will exit with the exposure in the same direction but in reverse.

### 3. Dove Prism

• It is a truncated version to reduce the weight and size of the orthogonal prism, being used mainly in a whole light.
• And also, it has the property of rotating the image twice as fast as the prime itself rotates around its longitudinal axis.

### 4. Amici’s Prism

• It is a truncated orthogonal prime with an added roof section on the hypotenuse side.
• It’s most common use has the effect of splitting the image in half and swapping the portions right to left.
• These prisms are expensive because we must keep the apical angle within approximately 3-4 arc sec.
• Otherwise, a bothersome double image will result. It is often used in a simple telescope system to correct for lens reversal.

### 5. Penta prism

• It will deflect the beam by 90º without affecting the orientation of the image. Note that two of its surfaces must be silver.
• These prisms are as reflectors at the ends of short-range finders.

### 6. Leman-Springer prism

• It has a 90º roof.
• The line of sight moves without deviating, but the image emerging has an orientation to the right and 180º of rotation.
• Therefore the prism can be used to straighten images in telescopic systems, for example, rifle sights.

### 7. Rhomboid prism

• It has the characteristic of shifting the line of sight without producing any angular deviation or changes in image orientation.