Physics · Wave optics: wavefront and Huygens' Principle, laws of reflection and refraction using Huygens principle

Ray optics fail when the size of the obstacle is :

Ray optics fail when the size of the obstacle is :

  • A. 5
  • B. 3
  • C. less than the wavelength of light
  • D. \( (a) \) and \( (b) \) both

Step-by-step solution

Ray optics (geometrical optics) assumes that light travels in straight lines and is valid when the size of obstacles or apertures is much larger than the wavelength of light. When the obstacle size becomes comparable to or smaller than the wavelength, diffraction effects dominate, and ray optics fails. Hence, the condition for failure is size less than the wavelength.
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