A lens made of glass whose index of refraction is 1.60 has a focal length of +20 cm in air. Its focal length in water, whose refractive index is 1.33, will be
a)
Three times longer than in air
b)
Two times longer than in air
c)
Same as in air
d)
None of the above
A lens made of glass whose index of refraction is 1.60 has a focal length of +20 cm in air. Its focal length in water, whose refractive index is 1.33, will be
a)
Three times longer than in air
b)
Two times longer than in air
c)
Same as in air
d)
None of the above
Question ID - 152217 | SaraNextGen Top Answer
A lens made of glass whose index of refraction is 1.60 has a focal length of +20 cm in air. Its focal length in water, whose refractive index is 1.33, will be
a)
Three times longer than in air
b)
Two times longer than in air
c)
Same as in air
d)
None of the above
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A lens made of glass whose index of refraction is 1.60 has a focal length of +20 cm in air. Its focal length in water, whose refractive index is 1.33, will be |
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a) |
Three times longer than in air |
b) |
Two times longer than in air |
|
c) |
Same as in air |
d) |
None of the above |
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(a) Given that, the refractive index of the lens wrt air,
And the refractive index of water wrt air The focal length of the lens in air, We know that for a lens
When the lens is in the air
When the lens is in the water
On dividing Eq. (i) by Eq. (ii), we get
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