Question

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A laser of 690nm hits a hair strand. This forms a pattern of alternating bright and dark lines on the screen. After measuring the distance from the central bright line to each mth dark line and the angle at which the dark line is observed the graph sine vs. m was built. What is the thickness of the hair, if the trendline equation of the graph is Y = 0.012 x? 87.6um 57.5pm O A. 73.4um O c. 157um D. В. O ES7Sum

Answer 1

Answer :--

as we know that the position of the fringe is given as

so the slope of the above graph will be

$\frac{sin\theta}{m}= 0.012$

• $dsin\theta = m\lambda$
• $sin\theta= \frac{\lambda}{d}m$............................(1)
• given equation of the graph of sin$\theta$ vs. m is --
• Y= 0.012X ............................(2)
• $\frac{\lambda}{d} = 0.012$
• $d= \frac{\lambda}{0.012}$
• $d= \frac{690 \times 10^{-9}}{0.012}$
• $d=57.5 \mu m$.\
• so th option (c) is correct .