Question

If $\omega$ is the dispersive power and $f$ is the mean focal length, then the longitudinal chromatic aberration is :

• A. $\frac{\omega }{f}$
• B. $\omega f$
• C. $\frac{\omega f}{2}$
• D. $2\omega$f

Answer 1

Answer: (B)

$\omega f$

Longitudinal chromatic aberration occurs if a lens can not focus different colors in the same focal plane. It is caused by straight incident light. The foci of the different colors lie at different points in the longitudinal direction along the optical axis.

The longitudinal chromatic aberration is defined as the product of the dispersion power and the mean focal length.
Hence, $c=\omega f$