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Light Waves — Physics STD 12 Science — Question

Bihar BoardEnglish MediumSTD 12 SciencePhysicsLight Waves2 Marks
Question
In a double slit interference experiment, the separation between the slits is 1.0mm, the wavelength of light used is 5.0 × 10-7m and the distance of the screen from the slits is 1.0m.
  1. Find the distance of the centre of the first minimum from the centre of the central maximum.
  2. How many bright fringes are formed in one centimeter width on the screen?
✓

Answer

Given that, d = 1mm = 10-3m, D = 1m.
So, fringe with $=\frac{\text{D}\lambda}{\text{d}}=0.5\text{mm}.$
  1. So, distance of centre of first minimum from centre of central maximum $=\frac{0.5}{2}\text{mm}=0.25\text{mm}$
  2. No. of fringes $\frac{10}{0.5}=20.$

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