A lens of power `+2` dioptres is placed in contact with a lens of power `-1` dioptre. The combination will behave like

Options

A. A convergent lens of focal length `50 cm`
B. A divergent lens of focal length `100 cm`
C. A convergent lens of focal length `100 cm`
D. A convergent lens of focal length `200 cm`

Answer

C

Explanation

`(1)/(f)-(1)/(f_(1))+(1)/(f_(2))=(P_(1))/(100)+(P_(2))/(100)=(1)/(100)impliesf=100cm`
`:.` A convergent lens of focal length `100 cm`.