In a double-slit experiment, two slits are 0.2 mm apart with a screen at a distance of 1m. The third bright fringe is found to be displaced at a distance of 7.5 mm from the central fringe. What is the value of the wavelength?
Correct answer: D. 0.0005 mm
- A. 0.03 mm
- B. 0.004 mm
- C. 0.00006 mm
- D. 0.0005 mm
Explanation
The explanation is given below:In the double slit experiment, the position of bright fringes is given by the equation:y = (mλD)/dWhere y is the displacement of the bright fringe from the central fringe, m is the order of the bright fringe, λ is the wavelength of light used, D is the distance from the slits to the screen, and d is the distance between the slits.In this problem, m = 3, d = 0.2 mm, D = 1 m, and y = 7.5 mm. Substituting these values into the above equation, we get:(3λ)/0.2 = 7.5/1000λ = (7.5/1000) x 0.2/3 = 0.0005 mmTherefore, the value of the wavelength is 0.0005 mm.
This question appeared on the NUMS 2019 (cancelled sitting) paper, which you can sit online with every answer explained.
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