Question

A 2.0 CM tall object is perpendicular to the principal axis of a convex lens of a focal length 10cm the distance of the object from the length is 15 cm find the image distance and height of the image

Answer 1

25 cm will be the height

Answer 2

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Object's size (h1) = 2 cm

Focal length of convex lens (f) = 10 cm

Object distance from the lens (u) = -15 cm

Image distance ( v) = ?

Image size (h2) = ?

We know,

1/v - 1/u= 1/f

1/v = 1/f + 1/u

1/v = 1/10 - 1/15

1/v = 1/30

Thus, v = 30 cm

Now, v = 30 cm, 'v' is positive, that means the image is formed on the right side of the lens. That's why it is REAL and INVERTED.

Now, magnification =?

Linear magnification (m) = Size of image / Size of object = h2 / h1 = v/u

m = h2/2 = 30/-15

m= h2 × -15 = 30×2

m = -15 h2 = 60

h2 = 60 / -15

h2 = -4 cm

Size of the image = -4 cm

It's in negative , that means that the image is INVERTED.