Question

If you were to use a green laser beam to measure the focal length, would you get the
same value? Does your answer bear on chromatic aberration in which a white object is
focused as a somewhat blurred color image?

If two lenses have exactly the same dimensions but have different indexes of refraction,
will their focal lengths be the same? Discuss

Answer 1

The index of refraction of differing wavelength (colors) is slightly different, so yes, the focus is slightly different for differing wavelengths. That changing focal length is chromatic aberration.

Answer 2

Cheers!