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Hi there.
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So for this problem, we are told that a jewel teeth hides a diamond by placing it on the bottom of a public swimming pool and he places a circular raft on the surface of the water directly above and centered over the diamond, as is shown in this figure.
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Now, if the surface of the water is calm and the pool is two meters deep, as is shown in the figure, we need to find the minimum diameter of the raft.
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That will prevent the diamond from being seen.
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So for this problem, we know that the circular raft covers the area of the surface through which light from the diamond could emerge.
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So does it must form the base of a cone with an apis at the diamond.
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And so we're going to put in here.
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So we need to have this right here.
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We're going to have something like this.
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And this angle right here, theta, is the angle that we are going to obtain.
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And then we're going to obtain this minimum radiance in here.
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And this, of course, this is the death age is the death of this.
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So whose half angle is, we know that that is theta, where theta is greater than, equal to the critical value or the critical angle...