Red light `I(lambda = 664 nm` in vacuum) is used in Young's experiment with the slits separated by a distance from the screen given by `D = 2.75 m.` Find the distance y on the screen between the central bright fringe and the third-order bright fringe.
Reasoning: This problem can be solved by the first using Eq. (i) to determine the value of `theta` that locates the third-order bright fringe. Then, trigonometry can be used to obatin the distance y.

Explanation

According to Eq. (i), we find
` theta = sin^(-1) ((m lambda)/(d)) = sin^-1 [(3(6.64 xx 10^(-9) m))/(1.20 xx 10^(-4) m]] = 0.951^(@)`
According to Fig. 2.33, the distance y can be calculated from
`tan theta = y//D`:
`y = D tan theta = 2.75 m tan 0.951^(@) = 0.0456 m`
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