A convex lens of power 3 D is held in contact with a concave lens of power -1 D. A parallel beam of light is made to fall on the combination. At what distance from the combination will the beam get focused?
Answers
Answer:
Yes it does split into it's constituent colours, although the degree to which it splits up depends upon several factors. This is called chromatic aberration.
Compared to a prism, the degree of splitting up of the white light is very less as lenses are usually thin, so light does not have enough time to split up.
The splitting of light happens due to the spherical shape of the lens. As, in case of convex lens, it is thinner at the top and thicker at the bottom, the light is converged more by the top(marginal rays) than the bottom(paraxial rays).
Here, you can see that the light splits up and intersects each other at different points. The marginal rays focus(mostly violet) a little ahead the actual focal length of the lens and paraxial(mostly red) a little behind. This type of aberration is called longitudinal or axial aberration as it happens along the principal axis.