What is a prism?
A solid piece of glass or plastic bounded by plane polished faces.
How is a prism represented in optics?
As a triangular section.
What are common uses of prisms in optics?
Dispersion in spectrometry and beam splitting in photometry and interferometry.
What is the base of a prism?
The unpolished face of the prism.
What are prisms used for in optometry?
To relieve symptoms from muscular defects in binocular vision such as heterophoria.
What are refracting faces?
The two faces containing AB and AC.
What is the principal section of a prism?
Section ABC used for constructing ray diagrams.
What is the apical angle of a prism?
The angle at A in the principal section.
What symbol represents the apical angle?
a
What happens when light enters a prism?
It is refracted at the first surface and again at the second surface.
What type of prisms are first considered in theory?
Prisms with large apical angle (>10°).
What type of prisms are used in optometry?
Prisms with small apical angle.
What happens to light as it passes through a prism?
It undergoes deviation at both refracting surfaces.
What do i₁ and i₁’ represent?
Angles of incidence and refraction at the first surface.
What do i₂ and i₂’ represent?
Angles of incidence and refraction at the second surface.
What are d₁ and d₂?
Deviations at the first and second surfaces.
What is total deviation (d)?
The sum of deviations at both surfaces.
Formula for deviation at first surface?
d₁ = i₁ − i₁’
Formula for deviation at second surface?
d₂ = i₂’ − i₂
Total deviation formula (basic)?
d = d₁ + d₂
Expanded total deviation formula?
d = (i₁ − i₁’) + (i₂’ − i₂)
Simplified deviation formula?
d = (i₁ + i₂’) − (i₁’ + i₂)
What relationship is used to simplify deviation?
a = i₁’ + i₂
Final formula for deviation of light by a prism?
d = (i₁ + i₂’) − a
