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Wave Optics — Physics STD 12 Science — Question

Gujarat BoardEnglish MediumSTD 12 SciencePhysicsWave Optics2 Marks
Question
State one feature by which the phenomenon of interference can be distinguished from that of diffraction.
A parallel beam of light of wavelength 600 nm is incident normally on a slit of width ‘a’. If the distance between the slit and the screen is 0.8 m and the distance of 2nd order maximum from the centre of the screen is 15 mm, calculate the width of the slit.
✓

Answer

The given features:-
Interference Diffraction
  1. Fringes of equal width
 Fringes of unequal width
  1. Fringes of equal intensity
 Fringes of decreasing intensity
  1. Due to superposition of two waves (wavefronts)
 Due to superposition of secondary wavefronts.
  1. Maximal at $\theta =\frac{\lambda}{\text{a}}$
 Minima at $\theta = \frac{\lambda}{\text{a}}$
$\text{ (Numerical : Formula}\text{ y} =\frac{(2\text{n} + 1)\lambda\text{D}}{2\text{a}}\text{ or } \frac{5\lambda\text{D}}{2\text{a}}$
Substitution and Result: $8 × 10^{-5}\ m$ or $0.08\ mm.$

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