Question

an object 6 cm high is placed at a distance of 36 cm from a diverging lens of focal length 12 cm .find the position and size of the image​

Answer 1

Answer:

Image is 9cm away from the lens and is 1.5 cm in height.

Explanation:

Concave lens :

Object height = 6cm.

Object distance = -36 cm ( as the object is

always kept on the left hand side ).

Focal length = -12 cm (negative for concave).

And we need to find the image distance and the image height.

From the lens formula ,

1/f = 1/v - 1/u

1/-12 =1/v - 1/-36

1/-12 = 1/v + 1/36

1/v = 1/-12 - 1/36

1/v = -1 /9 [ on solving ]

Therefore v= -9 cm.

Now magnification = v/u...

m = -9/-36.

Therefore m = 1/4 = 0.25

Also, m=Height of the image / Height of the object.

i.e. we have....

1/4 = h2/6

h2 = 1.5 cm.

Hence the image is virtual and erect, smaller in size by a factor of 0.25. The image is formed on the same side of the lens.