CBSE Class 12-science Answered

Two postulates of relativity on which Einstein’s theory is based are:

(1)   The relativity postulate:

The laws of physics are the same for observers in all inertial reference. No one frame is preferred over any other.

This postulate does not say that the measured values f all physical quantities are the same for all inertial observers; most are not the same.

It is the laws of physics, which relate these measurements to one another that are the same.

(2)   The speed of light postulate:

The speed of light in vacuum has the same value c in all direction and in all inertial reference frames.

Light happens to travel at this ultimate speed c.  No entity that carries energy or information can exceed this limit. No particle that has mass can actually reach speed c.