Question

Which one of the following spherical lenses (shown with radius of curvature) doesn't exihibit dispersion?

• A.
• B.
• C.
• D.

Answer 1

The correct option is C

Dispersion of light would not take place, if the angular deviation produced at the two refracting surfaces of lens are equal in magnitude and opposite direction, such that white light does not get split.
$\Rightarrow$ For plano convex and plano concave lens, the deviation will differ hugely due to difference in radius of curvature of two surfaces $(R$ and $\infty )$.


The shown lens has equal curvature and deviation produced at each surface will be opposite (rarer to denser & denser to rarer).

Why this question? Tip: Apply the concept of refraction at spherical surface along with net deviation produced.