Question

The focal length of a converging lens is measured for the violet, green and red colours. It is respectively $f_v,f_g,f_r$. We will find that

• A. $f_g=f_r$
• B. $f_v>f_r$
• C. $f_v<f_r$
• D. $f_g>f_r$

Answer 1

The correct option is C

$f_v<f_r$

Explanation

1. Dispersion of light says that the refractive index of the medium is dependent upon the wavelength of the light.
2. We know that the red colour of light has the greatest wavelength and hence refractive index will be lesser and will bend less than green and violet.
3. The Colour of light which bends less will have a greater focal length for converging lens.

So, the most suitable option from the given options is (c) $f_v<f_r$