Page 2 - Lesson note refraction through prism

 The angle of incidence.
 The refracting angle of the prism.
 Refractive index of the material used in the prism.
 The wavelength of the light ray.

The smallest angle through which light is bent by an optical element or system. In a
prism, the angle of deviation is a minimum if the incident and exiting rays form
equal angles with the prism faces.

The condition for minimum deviation through a prism is that angle of incidence (i)
is equal to angle of emergence ( e). In that case, the refracted ray
EF becomes parallel to the base bC of the prism.

Violet light has the maximum refractive index and least speed when travelling
through a medium since it has the shortest wavelength. Thus, it bends most upon
incidence and has maximum deviation.

Dispersion of light
In 1665, Isaac Newton discovered that white light consists of seven colours. He
found that if a beam of white light is passed through glass prism then it will split in to
seven colours. These colours are red, orange, yellow, green, blue, indigo and violet
(VIBGYOR).

Spectrum of white light: The band of seven colours formed when a beam of white
light is passes through a glass prism is called spectrum of white light.
Dispersion of light: The splitting of white light into seven colours on passing through
a transparent medium is called dispersion of light.
The dispersion of white light happens because the angle of refraction of lights of
different colours is different while passing through the transparent medium. For
example, red colour deviates least and is formed at the upper part of the spectrum
and violet colour is deviated maximum and is formed at the bottom of the spectrum.

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