Question

a person with a myopic eye cannot see objects beyond 1.2 metre directly what should be the type of the corrective lens used what would be its power

Answer 1

The person should use a concave lens with suitable focal length and the power may be -0.63 D....

Answer 2

Hey Friend,

Since the person suffers from Myopia, the corrective lens will be concave or diverging lens.

Given, that the person can't see objects beyond 1.2 m directly. 
So, in order to view the distances beyond 1.2 m, the focal length of the lens should be 1.2 m.

Power of lens = 1 /  focal length (in meter)
P = 1/(-1.2) 
P = -0.83 Diopter

Therefore the power of the lens should be - 0.83 D

Hope it helps