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Depth of a completely filled well is 11 m and the refractive index of water is 1.33. If viewed normally from top, by how much height would the bottom of the well appear to be shifted up?

Asked in GSEB Board March 2019 · Snell's law, slabs and apparent depth

• (1) 2.73 m
• (2) 11 m
• (3) 4.13 m
• (4) 1.37 m

Step-by-step solution

Why the other options are wrong

• (2) comes from the full depth of the well, not the shift. The bottom is lifted by only about a quarter of the depth.
• (3) 4.13 m is (5.5)/(1.33), carried over from the 5.5 m version of this question. For an 11 m well the apparent depth is (11)/(1.33)=8.27 m and the shift is 11-8.27=2.73 m.
• (4) 1.37 m is the shift for a 5.5 m well. The shift is proportional to the depth, so doubling the depth doubles it.

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