Question
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Answer (Detailed Solution Below)
Option 1 : $20\ \text{cm}$, $+5\ \text{D}$ / $20\ \text{cm}$, $+5\ \text{D}$
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Detailed Solution
सही उत्तर $20\ \text{cm}$, $+5\ \text{D}$ / $20\ \text{cm}$, $+5\ \text{D}$ है।
Key Points
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prepsnap.in • Part -AQuestion:
A biconvex lens has radii of curvature $20\ \text{cm}$ each and $n = 1.5$. Its focal length and power are / एक उभयोत्तल लेंस की वक्रता त्रिज्याएँ $20\ \text{cm}$ हैं तथा $n = 1.5$ है। इसकी फोकस दूरी तथा क्षमता हैं
1.
$20\ \text{cm}$, $+5\ \text{D}$ / $20\ \text{cm}$, $+5\ \text{D}$
2.
$40\ \text{cm}$, $+2.5\ \text{D}$ / $40\ \text{cm}$, $+2.5\ \text{D}$
3.
$10\ \text{cm}$, $+10\ \text{D}$ / $10\ \text{cm}$, $+10\ \text{D}$
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$20\ \text{cm}$, $-5\ \text{D}$ / $20\ \text{cm}$, $-5\ \text{D}$
Correct Answer: $20\ \text{cm}$, $+5\ \text{D}$ / $20\ \text{cm}$, $+5\ \text{D}$
$1/f = (1.5 - 1)(1/20 + 1/20) = 0.05$, so $f = 20\ \text{cm}$ and $P = 100/20 = 5\ \text{D}$. / $1/f = (1.5 - 1)(1/20 + 1/20) = 0.05$, अतः $f = 20\ \text{cm}$ तथा $P = 100/20 = 5\ \text{D}$।
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