Question

Define magnification. Write the sign convention used for expressing it and find magnification formed by a concave lens of focal length 20 cm and the object is at 15cm

Answer 1

Magnification is the ratio of the image distance to the object distance. On the other hand, magnification can be defined as the ratio of the image height to the object height.

If the magnification is negative sign, it means that the linear magnification creates a real image which is inverted. And if its sign is positive, then the image is virtual and erect.

We know,

1/v + 1/u = 1/f

⇒1/v = -1/20 + 1/15

⇒1/v = (-3+2)/60

⇒1/v = -1/60

⇒v = -60 cm

Now, magnification = v/u

⇒M = -60/15

⇒M = -4

So, the image formed is real and inverted.

Answer 2

Answer:

magnification is a process of enlarge the apparent size of object