Question

An object of height 5cm is placed in front of concave mirror of focal length 10cm and a real image of height 10cm is formed . Find the position of image

Answer 1

Answer:

15CM

Explanation:

Y/X = 2 , X = Y/2

1/Y + 1/X = 1/F

Y/F = Y/X + 1 = 2+1 = 3

Y = 3F = 15 CM

Answer 2

Answer: Given h= 5cm; f= -10cm h₁ = -10cm (h- height of the object ; h₁- Height of the image) and magnification is given by

m= h₁/ h

m= -10/5 m=-2 (h₁ is taken negative because the image is formed below the principal axis and according to the sign convention it has to be taken negative)

and also

m= -v/u so -2 =-v/u v=2u

substitute the given value in the mirror formula

1/f=1/u+ 1/v

1/-10 = 1/u+1/2u

1/-10 = 3u/2u x u

1/-10 3/2u

2u= -30 u= -15cm

and we have v=2u

therefore v=2*-15

v= -30cm

therefore the distance of the image from the mirror is -30cm

Explanation: Note that the image is formed below the principle axis and is at a distance of 30cm on the same side of the mirror.