Question

if the power of the convex lens is 4D then find the focal length of that lens

Answer 1

P=1/f

P=4d

4=1/f

F=1/4m =0.75m

Therefore f=75 cm

Answer 2

P= 1/f

P=4

4=1/f

After cross multiplication

4f=1

F=1/4

F=0.75m or 75cm