For a concave lens the distance between image and object is 10cm and magnification is 1/4. Focal length of the lens is
 hiii,
 
 
 Here is the solution to the question
 
 
 Distance between object and image = 10 cm
 
 
 Magnification = height of image / height of object =  v/u
 
 
 M= 1/4 (given)
 
 m= v/u =1/4
 
 u = 4v
 
 
 u-v = 10cm
 
 so,
 
 4v-v = 10 cm
 
 v= 10/3 cm
 
 hence u =40/3 cm
 
 
 now applying the lens formula
 
 
 1/f = 1/v -1/u
 
 = -3/10 + 3/40
 
 = - 4.4 cm
 
 
 therefore the focal length is -4.4cm
 
 
 I hope you understand the solution.
 
 Feel free to revert back for any queries.
 
 
 Thank you!!!
								
              
              
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