Question

In which condition the lens combination will act as a plane glass sheet?

Answer 1

when the power of convex lens and concave lens will be same.
for example :power of Concave lens = -4
power of convex lens =+ 4
and as we know to get the power of combined lens we find out the algebraic sum of individual powers so if we will combine them we will get 0 as answer.

Answer 2

A lens will act as a plane glass sheet when one of the lenses is convex and the other is concave with the power.

Explanation:

• Following are some of the terminologies which one needs to remember to solve the above question.
• A lens is a transparent polished body bounded on two sides by curved surfaces. In particular, one of the surfaces may be a plane.
• The two types of basic lenses are concave lenses and convex lenses.
• A concave lens is a lens that diverges a straight light beam from the source to a diminished, upright, virtual image.
• However, A convex lens is a lens that converges rays of light that convey parallel to its principal axis (i.e. converges the incident rays towards the principal axis)
• The focal length of a lens is equal to half the length of the radius of curvature of the lens i.e., f = R/2
• The power of a lens is defined as the reciprocal of its focal length. It is represented by the letter P. The power P of a lens of focal length f (in m) is given by. P=1f. The SI unit of power of a lens is 'Dioptre'.
• Now, when we build a system, where the incident light rays are made to pass through both the lenses i.e., concave and convex lenses of equal power the convergence and divergence would nullify each other and the system will behave as a plane sheet of glass.

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