What will happen to the FOCAL LENGTH if CONCAVE LENS or a CONVEX LENS is IMMERSED in WATER.
Answers
Answered by
4
there will be no effect on focal length.
DeepanshuSrivastava:
Why?
Answered by
3
I would think that it gets bigger.
Explanation:
We know from the famous Lensmaker´s Formula that:
1f=nl−nmnm(1R1+1R2)
where:
f= focal length;
nl= index of refraction of lens (glass);
nm= index od refraction of the medim (in which the lens is placed);
R1andR2 radii of curvature of lens surfaces.
Consider an exampe:
A lens that has a focal length of +20cmhas equal radii, so that R1=R2=R, and is made of glass of nl=1.6; you place it into water (nm=1.33). Remember that we can consider the index of air as 1. We have:
In air:
120=1.6−11(2R)
In water:
1f'=1.6−1.331.33(2R)
substitute one into the other for (2R):
120(1.6−1)=1.33f'(1.6−1.33)
rearranging:
f'=1.3320(1.6−1)1.6−1.33≈60cm
Explanation:
We know from the famous Lensmaker´s Formula that:
1f=nl−nmnm(1R1+1R2)
where:
f= focal length;
nl= index of refraction of lens (glass);
nm= index od refraction of the medim (in which the lens is placed);
R1andR2 radii of curvature of lens surfaces.
Consider an exampe:
A lens that has a focal length of +20cmhas equal radii, so that R1=R2=R, and is made of glass of nl=1.6; you place it into water (nm=1.33). Remember that we can consider the index of air as 1. We have:
In air:
120=1.6−11(2R)
In water:
1f'=1.6−1.331.33(2R)
substitute one into the other for (2R):
120(1.6−1)=1.33f'(1.6−1.33)
rearranging:
f'=1.3320(1.6−1)1.6−1.33≈60cm
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