Question

An object is placed at a distance of 25cm away from a converging lens of focal length 20cm .Discus the effect on the nature and position of the image if the position of the object changes from 25cm to 15cm .justify your answer without using lens formula.​

Answer 1

Answer:

Image distance is 100 cm.

Explanation:

object distance = p = 25 cm

Image distance = q = find out

focal length = f = 20 cm

Solution

Mirror formula is given as

1/f = 1/p + 1/q

1/20 = 1/25 +1/q

0.05 = 0.04 +1/q

1/q = 0.01

q = 100 cm

So a real image is formed in front of the mirror at a distance 100 cm from the mirror.

b)

If object is displaced from 25 cm to 15

It appears that object distance is less than the focal length (object falls in the focal length). So a virtual image is formed behind the mirror.

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Answer 2

Answer:

Explanation:

we kn tht focal length is 20cm and obj distance is 25cm.

if the u (obj distance) is 15cm, the object lies b/w focus and principal axis.

now using RAY DIAGRAM, the nature of the image is virtual and erect, image size is enlarged and position of image is behind the mirror

we need not do any calculations coz the questions says us without using lens formula.