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Please help me with this problem.

# A small air bubble in a sphere of 8 cm diameter of a substance having refractive index 1.4 appears to be 2 cm from the surface when looking along the diameter. Find the true position of the bubble.

I solved it in the following way:

Here n1 = 1, n2 = 1.4, v = -2 cm(Virtual image), R = + 4 cm

n2/v + n1/u = (n2 – n1)/R

1.4/-2 + 1/u = 0.4/4

1/u = 0.1 + 0.7 = 0.8

u = 1/0.8

u = 1.25 cm

But the book answer is 2.33 cm. But I get this answer if I do it in a different way.

Here n1 = 1, n2 = 1.4, v = -2 cm(Virtual image), R = + 4 cm

n1/v + n2/u = (n1 – n2)/R

1/-2 + 1.4/u = (1.4 – 1)/4

1.4/u = 0.1 + 0.5 = 0.6

u = 1.4/0.6

u = 2.33 cm

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# Homework Help: Air bubble inside a glass sphere problem

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