Question

If we want the consideration of lenses used for achromatism to behave as a convergent lens then the convex lens should be made of
Given, ${\omega }_{flint}>{\omega }_{crown}$ [$\omega$ is dispersion power]

• A. Flint glass
• B. Crown glass
• C. Either Flint glass or crown glass
• D. None of these

Answer 1

The correct option is A Flint glass

If we want the combination to behave as a convergent lens, then convex lens should have lesser focal length or its dispersive power should be more.
Thus, convex lens should be made of flint glass and concave lens of crown glass.