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General
Easy
Question
A man starting from point P crosses a 4 km wide lagoon and reaches point Q in the shortest possible time by the path shown in the figure. If the person swims at a speed of 3 km/hr and walks at a speed of 4 km/hr, then his time of journey is (µsaltwater = 4/3) :
- 4hr, 10 min.
- 4 hr and 30 min.
- 3 hr and 50 min
- 5 hr and 10 min.
The correct answer is: 4hr, 10 min.
As we know that light travels in a path such as to reach from one point to another in shortest possible time. Therefore, the man must travel along that path on which light would have travelled in moving from P to Q.
By Snell's law ;
From P to A :
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