The focal lengths of convex lens for red and blue light are 100 cm and 96.8 cm respectively. The dispersive power of material of lens is

Options

A. 0.968
B. 0.98
C. 0.0325
D. 0.325

Answer

c

Explanation

We have , `f_(r) -f_(b)=omegaf_(y)`
`omega=(f_(r)-f_(b))/(f_(y))`
Here , `f_(r)=100cm`
`f_(b)=96.8cm`
`f_(y)=sqrt(f_(b)xxf_(r))`
`=sqrt(96.8xx100)`
`=98cm`
`therefore` Dispersive power
`omega=(f_(r)-f_(b))/(f_(y))`
`=(100-96.8)/(98)`
`=(3.2)/(98)=0.0325`