A prism of a certain angle deviates the red and blue rays by `8^@` and `12^@` respectively. Another prism of the same angle deviates the red and blue rays by `10^@` and `14^@` respectively. The prisms are small angled and made of different materials. The dispersive powers of the materials of the prisms are in the ratio

Options

A. `5:6`
B. `9:11`
C. `6:5`
D. `11:9`

Answer

C

Explanation

For one prism,
`omega_(1)=(delta_(B)-delta_(R))/(delta)=(12-8)/(10)( :.delta=(delta_(B)+delta_(R))/(2))`
`omega_(1)=(4)/(10)`
For the prism,
`omega_(2)=(delta_(B)-delta_(R))/(delta)=(14-10)/(12)( :.delta=(14+10)/(2))`
`omega_(2)=(4)/(12)=(1)/(3)`
`:.(omega_(1))/(omega_(2))=(4xx3)/(10xx1)` or `(omega_(1))/(omega_(2))=(12)/(10)=(6)/(5)`