Question

Ray optics is valid when characteristic dimension are

• A. much smaller than wavelength of light.
• B. of same order as wavelength of light
• C. much larger than wavelength of light
• D. none of the above

Answer 1

The correct option is C much larger than wavelength of light

Ray optics is valid when characteristic dimension are much larger than wavelength of light . The size of obstacle must be much larger than the wavelength of light. If wavelength is comparable to the size of object, then diffraction could happen, but it cannot be explained using ray optics, it will require wave theory of light.