alleryA real image of magnification 2 is formed by a convex lens of focal length 10 cm. Object distance is:
A5 cm
B15 cm
C20 cm
D30 cm
Answer & Solution
Correct answer: B. 15 cm
1. For a real image m = -2, so v = -2u.
2. Lens formula: 1/v - 1/u = 1/f.
3. Substitute v = -2u and f = +10: 1/(-2u) - 1/u = 1/10.
4. = -1/(2u) - 1/u = -3 / (2u) = 1/10.
5. So 2u = -30, giving u = -15 cm.
6. Object distance magnitude is 15 cm.
_Source: Selina Concise Physics ICSE Class 10, Ch 5 'Refraction through a Lens' (aplustopper.com extract)_
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