Dispersion by a Prism: If a prism is placed in a room and a narrow beam of white light is allowed to fall on one of its refracting faces, it is found that light coming out from the other face of the prism is split in to seven colors i.e violet, indigo, blue, green, yellow, orange and red. This phenomenon is called dispersion at light. The phenomenon of splitting of white light into its seven constituent colors is called dispersion of light.
Dispersion power: The dispersive power ω of a prism is the ratio of angular dispersion to the deviation of the mean ray u yellow color i.e,
Dispersive power ωat prism depends only on the nature of the material of the prism. However, angular dispersion and mean deviation both depend on nature of prism material and the angle at prism.

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