Question

Why does light travel in a straight line?

Answer 1

Light does not travel in a straight path. It travels as a wave. However as the wavelength is very small, it looks like it travels in a straight line. Also when light travels from one medium to another, it bends. It is called refraction. Now under normal circumstances, light does seem to travel in a straight line. Here’s why:

• Light unlike sound does not need a medium to propagate. So it doesnot get carried away due to disturbances in the medium in which it is propagating. But sound does get carried away by wind etc as wind ‘carries’ the sound.
• Light being mass less, remains unaffected by gravity (under normal conditions not taking into account the gravity of stars and gravitational lensing).
• As the wavelength of light is very small, it cannot bend around corners, like sound.
• Otherwise you can understand it by a small experiment.In a dusty atmosphere it is sometimes possible to see light travelling. The fact that light travels in a straight path can be demonstrated by putting an object in its path. If the object is opaque and casts a dark shadow then it shows that light travels in a straight line.