Question

an object of length 2 cm is placed perpendicular to the principle axis of a convex lens of focal length 12 cm , find the size of the image if the object is at a distance of 8 cm from the lens.

Answer 1

Answer :-

Using mirror formula :

• 1/v - 1/u = 1/f

Where,

• object distance (u) = -8 cm
• focal length (f) = 12 cm

Substituting,

• 1/v = 1/12 + 1/-8
• 1/v = -2 + 3/-24
• 1/v = 1/-24
• v = -24 cm

So, magnification :

• m = v/u
• m = -24/-8
• m = 3

Also,

• m = h2/h1

Thus,

• h2 = 3h1
• h2 = 3 × 2 cm
• h2 = 6 cm

• Positive sign shows that the image is erect.