The focal length of a thin convex lens for red and blue colours is 100.5 cm and 99.5 cm .The dispersive power of the lens is
The focal length of a thin convex lens for red and blue colours is 100.5 cm and 99.5 cm .The dispersive power of the lens is
A. 0.01
B. 0.02
C. 1.005
D. 0.995
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Correct Answer - A
(a) We have, `f_(y)=sqrt(f_(R)f_(b))`
`f_(y)=sqrt(100.5xx99.5)=99.99`
Also, omega=`(f_(R)-f_(b))/(f_(y))=(100.5-99.5)/99.99`
Dispersive power,omega=`1/99.99=0.01`
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