Question

A concave mirror of focal length 30 cm is placed at distance of 90cm from the wall, How far from the wall should an object so placed to get real image on Wall?

Answer 1

A concave mirror of focal length 30 cm is placed at distance of 90cm from the wall, How far from the wall should an object so placed to get real image on wall?

Good question,

Here is your perfect answer!

Here v = - 90cm,

f = - 30cm

(sign convention)

Applying Mirror's formula,

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

=) 1/u = - 1/30 - (-1/90)

=) 1/u = - 1/45cm

=) u = - 45cm,

Hence the object is at distance of (90-45) = 45cm from the wall.

Answer 2

Answer:

just applying the mirrors formula