Question

a concave mirror of focal length 10 cm is kept in front of an object at a distance of 50 cm in front of it if the object 1 cm high what will be the size of image

Answer 1

f = -10 cm 
u = -50 cm 
h1 = 1 cm 
v = ? 

so , 1/f = 1/v + 1/u 
1/ -10 = 1/v + 1/ -50 
-1/10 = 1/v - 1/50 
-1/10 + 1/50 = 1/v
-5+1/50 = 1/v 
-4/50 = 1/v 
-2/25 = 1/v 
  
so v= - 25/2 cm 

now h1/h2 = -v/u 

putting the values 

 1/h2 = - ( -25/2) / 50 
1/h2 = 25/2 * 1/50 
 1/h2 = 1/4 

therefore h2 = 4 cm