Assertion -A double convex lens - -1-5 has focal length 10 cm- When immersed in water - -4-3 -its focal length becomes 40 cm- Reason- 1f- l- m-m 1R1-1R2

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Assertion :A ...

Question

Assertion :A double convex lens $(μ = 1.5)$ has focal length 10 cm. When immersed in water $(μ = 4 / 3)$ ,its focal length becomes 40 cm. Reason: $\frac{1}{f} = \frac{μ_{l} - μ_{m}}{μ_{m}} (\frac{1}{R_{1}} - \frac{1}{R_{2}})$

Both Assertion and Reason are correct and Reason is the correct explanation for Assertion

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Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion

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Assertion is correct but Reason is incorrect

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Both Assertion and Reason are incorrect

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Solution

The correct option is A Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
The focal length of the lens when it is immersed in water is 4 times than the focal length of the lens in air.
i.e., $f_{w a t e r} = 4 f_{a i r}$

Given that $f_{a i r} = 10 c m$

$⟹$ $f_{w a t e r} = 4 \times 10 = 40 c m$

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Assertion :A double convex lens (μ=1.5) has focal length 10 cm. When immersed in water (μ=4/3),its focal length becomes 40 cm. Reason: 1f=μl−μmμm(1R1−1R2)

The correct option is A Both Assertion and Reason are correct and Reason is the correct explanation for AssertionThe focal length of the lens when it is immersed in water is 4 times than the focal length of the lens in air.i.e., fwater=4fairGiven that fair=10cm⟹ fwater=4×10=40cm

Assertion :A double convex lens $(μ = 1.5)$ has focal length 10 cm. When immersed in water $(μ = 4 / 3)$ ,its focal length becomes 40 cm. Reason: $\frac{1}{f} = \frac{μ_{l} - μ_{m}}{μ_{m}} (\frac{1}{R_{1}} - \frac{1}{R_{2}})$