Question

where one should keep the object in front of a concave mirror so that two times magnified real image is obtained. focus of the mirror is 40cm?

Answer 1

where one should keep the object in front of a concave mirror so that two times magnified real image is obtained. focus of the mirror is 40cm?

Good question,

Here is your perfect answer!

Here f = - 40cm,

m(magnification) = - 2

=) - v/u = - 2

=) v = 2u

=) 1/v + 1/u + 1/-40

=) 1/2u + 1/u = - 1/40

=) 3/2u = - 1/40

=) u = - 60cm,

Hence one should keep the object 60 cm far in front of a concave mirror so that two times magnified real image is obtained.

Answer 2

F = -40cm

To obtain a magnifies image which is 2 times the large a the object height:

-v/u = m

-v/u = 2

1/v+1/u = 1/40

-v/v + -v/u = -v/-40(multiply throughout by -v)

-1 -2 = v/40

-3 = v/40

v = -120

-2 = -v/u

-2 = 120/u  

u = -60cm

The object should be placed at 60cm