Given,
Power p = 1.5 D
focal length f = ?
Using the formula ,
P= 1/f
f = 1/P
f = -1/5
f = -0.66m
f = -66 cm.
here the focal length is in negative , lens must be concave.
the focal length of the given concave lens is 66 cm. A concave lens is a lens that possesses at least one surface that curves inwards. It is a diverging lens, meaning that it spreads out light rays that have been refracted through it. A concave lens is thinner at its centre than at its edges, and is used to correct short-sightedness (myopia).