Physics - Geometrical Optics Question with Solution | TestHub

The dispersive power ($\omega$) is given by $\omega =\frac{f_R-f_V}{f_Y}$, where $f_R$, $f_V$, and $f_Y$ are focal lengths for red, violet, and yellow (mean) light, respectively. The difference in focal length for violet and red light is $f_R-f_V=\omega \cdot f_Y$.

Given $\omega =0.04$ and $f_Y=10$ cm.

$f_R-f_V=0.04\times 10cm=0.4cm=4mm$.

The final answer is $\boxed{4}$.