Question

an object of hight 6 cm is placed peroendicular to the principal axis of a concave lens of focal length 5cm. use lens formula ti determine the position, size and nature of the image , if distance of the object from the lens is 10cm.

Answer 1

Hey Friend,

Applying the sign conventions of concave lens -

object height (ho) = 6 cm
focal length of lens (f) = - 5 cm
object distance (u) = - 10 cm

Let the image distance be 'v' cm and image height be 'hi' cm.

Applying lens formula 
1/f = 1/v - 1/u
1/(-10) = 1/v - 1/(-5)
1/v = 1/(-10) + 1/(-5)
1/v = 3/(-10)
v = - 10/3
v = - 3.33 cm

We know,
hi / ho = v / u
hi / 6 = -10/3 x 1/-10
hi = 6/3
hi = 2 cm

Since the height of image is smaller the height of object, image is diminished. Since, the height of image is positive, image is virtual and erect.

So, the image at formed at a distance of 3.33 cm from the lens. The image is 2 cm tall and is virtual, erect and diminished.

Hope it helps!