Question

3. A concave mirror produces a real image of size 3 times that of the object at a distance of 30 cm from the
pole of the mirror. Find the position of the object.
(Similar C.B.S.E. 2011)
[Ans. - 90 cm]
4. How far should an object be from the pole of a concave mirror of focal length 20 cm to form a real image
whose size is
th of the size of the object.
(Similar C.B.S.E. 2011) [Ans. 120 cm]



answer this and help me plz with full explanation​

Answer 1

this linked picture is of fourth question

3.Given: 

Object distance =u=-30cm(by sign convention)

v=?

height of object be =h cm

height of image=- 3h cm(real image)h=-v/u

m=height of image/height of object

⇒-3h/h = -v/u

h3=v/u

⇒v=uX3

∵u=-30cm

we get v=-30x3

=-90cm

Negative sign indicates that image formed is real and inverted at a distance of 90cm from mirror...

4.virtual image will be formed behind the concave mirror if the object is placed between pole and focus of the mirror.

The follwing figures explain the formation of images in a convex mirror when the object is placed in different positions in front of it.

●its figure is being attached at the starting

Answer 2

Answer:

hope this will help you