A concave refractive surface of a medium having refractive index `mu` produces a real image of an object (located outside the medium) irrespective of its location. Choose the correct option from the following.

Options

A. Always
B. May be if refractive index of surrounding medium is greater than `mu`
C. May be if refractive index of surrounding medium is less than `mu`
D. None of the above

Answer

D

Explanation

We have `(mu)/(v)-(mu_(1))/(-u)=(mu-mu_(1))/(-R)`
`(mu)/(v)=-(mu_(1))/(-u)+(mu_(1)-mu)/(R)`
`(mu)/(v)=(-mu_(1)R+mu_(1)u-muu)/(uR)`
`v=(muuR)/((mu_(1)-mu)u-mu_(1)R)`
For real image, v should be positive
So, `(mu_(1)-mu_(2))mu-mu_(1)R gt 0` for real image
i.e., `mu_(1)mu gt (mu_(1)R)/(u)`
or `mu_(1)(1-(R)/(u)) gt mu`
`mu_(1) gt mu[1-(R)/(u)]^(-1)`
which depends upon the location of object.