If final image after two refractions through the lens and one reflection from the mirror forms at the same point O. Refrative index of the material of the lens `mu=3//2`. Then find d.

Explanation

`(1)/(f)=(mu-1)((1)/(R_(1))-(1)/(R_(2)))=(1)/(40)`
`(1)/(v)-(1)/(u)=(1)/(f)rArr (1)/((d-30))-(1)/((-80))=(1)/(40)`
`rArrd=110cm`