A photographer uses his camera, whose lens has a 50 mm focal length, to focus on an object 1.5 m away. He then wants to take a picture of an object that is 30 cm away. How far must the lens move to focus on this second object?

The distance is

Explanation:

From the question we are told that

   The  focal length is  

Generally the lens equation is mathematically represented as  

At  image  distance  u =  1.5 m

=>      

=>

At  image  distance  

=>    

=>    

The distance the lens need to move is evaluate as

powerful computers now, not then