Kindly answer these questions.

Solution :

The answers of the question (ii) and (iii) are provided below. 

(ii) Defective near vision, v = -75cm

Now, lens formula for this,

1/v + 1/25 = 1/f

=> 1/(-75) + 1/25 = 1/f

=> 2/75 = 1/f

=> f = 75/2 cm

So, power of the lens, P = 1/f

=> P = (100/(75/2)) D

=> P = 2.667 D

(iii) Given P = 1D

f = 1m = 100cm
u = 25 cm 

Using lens formula,

1/v - 1/u = 1/f
1/v = 1/100 + (-1/25) 
1/v = 1 - 4/100
1/v = - 3/100
v = - 100/3
v = - 33.3 cm

Kindly post the different question in the different thread.