Question

 Find the nature, position and magnification of the images formed by a convex lens of focal length 0.20 m if the object is placed at a distance of: 

 0.15 m 

Answer 1

 u = -15 cm 
         f = 20  

Substituting these values in the lens formula, we get: 

`1/f=1/v-1/u` 

`1/20=1/v-1/-15` 

`1/20=1/v+1/15` 

`1/20-1/15=1/v` 

`1/v=(3-4)/60` 

`1/v=-1/60` 

v=-60 cm  

The image will be formed at a distance of 60 cm in front of the mirror. 

`m=v/u` 

⇒`m=(- 60)/-15` 

⇒m=4   

Magnification is positive; therefore, the image is virtual and 

erect.