When concave lens is immersed in water then its focal length will be?

Option 2 : It will decrease

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Explanation:

Power of a lens: It is the converging or diverging capacity of a lens. Given by:

P = 1/f

Where f = Focal length.

When a lens is immersed in water, focal length of lens increases.

• This is so because when light enters from a denser medium to a rarer medium, it bends away from the normal.
• As water is more denser medium than air, bending of light will be less in water.
• As a consequence focal length in water will be more as compared to focal length in air.

\(\frac{{{{\rm{f}}_{{\rm{liquid\;}}}}}}{{{{\rm{f}}_{{\rm{air\;}}}}}} = \frac{{{{\rm{n}}_{{\rm{ga}}}} - 1}}{{{{\rm{n}}_{{\rm{gl}}}} - 1}} = \frac{{{{\rm{n}}_{{\rm{ga}}}} - 1}}{{\left( {\frac{{{{\rm{n}}_{{\rm{ga}}}}}}{{{{\rm{n}}_{{\rm{la}}}}}} - 1} \right)}}\)

As focal length increases power of the lens will decrease.

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CBSE 10 - Physics

Asked by vpitliya42 | 21 Nov, 2022, 01:21: PM

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