Question

a bright object 50mm stands on the axis of concave mirror of focal length 100mm and at a distance of 300mm from the concave mirror how big will be the image?

Answer 1

Height of the object (h) = 50 mm

Focal lenght of the mirror (f) = -100 mm

Object distance (u) = -300 mm

1/v + 1/u = 1/f

1/v = 1/f - 1/u

1/v = 1/(-100) - 1/(-300)

1/v = -1/100 + 1/300

1/v = (-3 + 1)/300

1/v = -2/300

v = 300/-2

v = -150 mm

Therefore, the image will be formed 150 mm away from the pole.

magnification (m) = h '/h = - v/u

h ' = - (v)(h)/u

h ' = - (-150)(50) / (-300)

h ' = -7500/300

h ' = -25 mm

Therefore the height of the image will be 25 m

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