An object of height `2 cm` is held at a distance of `40 cm` in front of a concave lens of power `- 5D`. Find the size of the image?

Options

A. 2/3 cm
B. 4/3 cm
C. 7/8 cm
D. 2/5 cm

Answer

A

Explanation

Here, `h_(1) = 2cm, u= -40cm`,
`P= -5D, f= 100/-5 cm= -20cm`
From `(1)/(v) - 1/u= (1)/(f) , (1)/(v) = (1)/(f) + 1/u = 1/-20 + 1/-40 = -3/40`
`v= -40/3 = -13.3 cm , m= (h_(2))/(h_(1)) = v/u = (-40//3)/(-40) = 1/3 , h_(2) = (h_(1))/(3)= 2/3cm` .