Where should an object be placed before a convexlens of focal length 10 cm be placed to get avirtual image at a distance of 30 cm from the lens?(1) at 15 cm from the lens(2) at 7.5 cm from the lens(3) at 22.5 from the lens(4) at 30 cm from the lens
Question
Where should an object be placed before a convexlens of focal length 10 cm be placed to get avirtual image at a distance of 30 cm from the lens?(1) at 15 cm from the lens(2) at 7.5 cm from the lens(3) at 22.5 from the lens(4) at 30 cm from the lens
Solution
The lens formula, which relates the object distance (u), the image distance (v), and the focal length (f) of a lens, is given by:
1/f = 1/v - 1/u
We know that the focal length f is 10 cm and the image distance v is -30 cm (the negative sign indicates that the image is virtual and on the same side as the object).
Substituting these values into the lens formula gives:
1/10 = -1/30 - 1/u
Solving this equation for u gives:
1/u = 1/10 + 1/30 = 4/30 = 2/15
Therefore, u = 15/2 = 7.5 cm.
So, the object should be placed 7.5 cm from the lens. The correct answer is (2) at 7.5 cm from the lens.
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