A slit or an aperture diffracts light. Even then we say light travels in a straight line and ray optics is valid. Comment.

Show with an experiment that light travels in a straight line.

Light appears to travel in a straight lines,since

Why does light appear to travel in straight line inspite of its wave nature.

Answer the following questions: 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?