CBSE Class 12-science Answered

We know from Lens Maker's formula; 1/f = (U-1)(1/R1 -1/R2) where U is the refractive index of the material. If the wavelength increases refractive index decreases as, Wavelength = c/U where c is the speed of light. hence the focal length increases and as power is reciprocal of focal length it increases with the decrease in 'f'. So wavelength and power are inversely proportional to each other i.e. with the increase in wavelength power decreases and vice-versa. Using this relation we can draw a graph showing variation between power of lens and wavelength of the incident light.