Question

Two lenses have have power of i)+2D minus ii)-4 D. what is the nature and focal length of each lens? An object is kept at a distance of 100 cm from each of the above lenses. Calculate the 1)image distance2) magnification in each of two cases

Answer 1

Resultant Power of a lens is equal to the sum of the powers of the individual lenses.

Resultant power = + 2 dioptre + (-4 dioptre) = -2 dioptre

 

As the sign of the resultant power of the lens is negative it is a concave lens

Answer 2

+2-4=-2
here is the correct answer