Answer to Question #91464 in Optics for Umm e Aiman

Question

What would be the effect on focal length if different colours of light falls on a lens? The focal length would remain same or not?

Answer 1

 

The focal length will change. Chromatic aberration occurs when different wavelengths of light are focused at different distances from the lens. The focus of purple rays (most refracting) is closest to the lens, and the focus of red rays (the least refracted) located at the far end from the lens.