Answer the following question:
Ray optics is based on the assumption that light travels in a straight line. Diffraction effects (observed when light propagates through small apertures/slits or around small obstacles) disprove this assumption. Yet the ray optics assumption is so commonly used in understanding location and several other properties of images in optical instruments. What is the justification?
The ray optics assumption is used in understanding location and several other properties of images in optical instruments because in the commonly used optical instruments are large when compared to the wavelength of light. Thus, the diffraction, a phenomenon is not observed when light waves interact on such a macro level and there is no violation of rectilinear property of light.