A Thin Lens Has a Focal Length of 10

Multiple Choice

A thin lens has a focal length of 10.00 cm for red light.If the index of refraction for the lens material tends to decrease with increasing wavelength,what is the focal length of the lens for blue light?

A) also 10.00 cm
B) less that 10.00 cm
C) more than 10.00 cm
D) It depends on whether the lens is converging or diverging.