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16 votes
16 votes
The diagram shows rays of light from a point source, P, that reach a detector, D, along two paths. One path is a straight line, while the other is bent by reflection off a mirror. What is the value of b, correct to one decimal place? Assume that all the points in the diagram lie in the same plane.

User Hill
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2 Answers

14 votes
14 votes

Answer:

b = 3.6

Explanation:

User Sean Beanland
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3.2k points
22 votes
22 votes

This can solved using the cosine law which is:

c² = a² + b² - 2ab cos θ

Using the values given from the problem

6² = b² + b² - 2bb cos 112.62

And solving for b

36 = 2b² - 2b² cos 112.62

b = 3.6

The answer is the 3rd option.

User Ram Ghadiyaram
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2.7k points