Question

An converging mirror of focal length 20cm forms an image which is two times the size of the object. Calculate two possible distances of the object from the mirror.

Answer 1

Hi....

1/f = 1/v + 1/u

focal length (f) = -20 cm
v = image distance 
u=object distance 

now, according to the given question ,

hi / ho = - V/U = 2 

hi = 2ho also v = -2u 

since we got v = -2u

Thus;

-1/20 = -1/2u + 1/u

-1/20 = -1 + 2 / 2u

-1/20 = 1/2u

2u = - 20

u = -10 cm

Hope this helps u!!

Answer 2

#Ur Ans
__________

mirror formula is 

1/f = 1/v + 1/u ---------(1)

where f → focal length = -20 cm

v =>image distance 
u=> object distance 

now, according to the given question ,

hi / ho = - V/U = 2 

⇒ hi = 2ho also v = -2u 

since we got v = -2u -----(2)

now by substituting equation (2) in (1) Thus

@⇒ -1/20 = -1/2u + 1/u

@⇒ -1/20 = -1 + 2 / 2u

@⇒ -1/20 = 1/2u 

@⇒ 2u = - 20 

@⇒ u = -10 cm 


Hope it's helpful ✌☺