A lens can be taken as a group of prism.
Answers
Answer:
Explanation:
A prism is a wedge of glass (plastic, whatever) that refracts light, causing it’s path to bend. The greater angle the wedge has, the greater the degree of deviation (also related to the refractive index (the optical density) of the glass or other material).
For narrow-angle prisms this mainly just shifts the resultant position of the image (or from the position of someone viewing that image, it shifts the apparent position of the object).
But because different length wavelengths are refracted/bent different amounts then for larger angle prisms it also causes the different
wavelengths to become spread out in the image, thus producing a spectrum of colours from “white” light.
A convex (+) or concave (-) lens can be thought of as two end-on prisms.
Unless light is passing through the optical centre of a lens where the surfaces are parallel to each other (thus yielding no prismatic effect at the centre), light passing through the periphery of a lens experiences Prismatic effect.
The further from the flat lens centre, the greater the angle between the opposing surfaces - thus bending light more and more, and this is why lenses focus light. This can be easily visualised with fresnel lenses where the surfaces have incrementally greater gradations of angle, removing the needless bulk between.