Question

search size of image of an object by a mirror having a focal length of 20cm observed to be reduced to one third of its size at what distance the object has been placed from the mirror what is the nature of the image and mirror​

Answer 1

Answer:

Solution :

If the mirror is concave, f=−20cm,m=−13

As m=−vu∴−13=−vu,v=u3

As 1v+1u=1f

3u+1u=−120oru=−80cm.

Image would be real and inverted.

If the mirror is convex, f=+20cm,m=+13

As m=−vu∴13=−vu,v=−u3

1v+1u=1f∴−3u+1u=120oru=−40cm.

Image would be virtual and erect.

Answer 2

Explanation:

Using magnification formula, m = - vu = 13 v = - u3 From mirror formula, 1v + 1u = 1f From above two equations, 3-u + 1-u = 120 u = - 80 cm So, the object ...