Second Postulate Of Special Relativity: "Speed of light in vacuum remains same for all inertial reference frames" The speed of light in glass is 2 x 10^8 m/s . So how is now the above postulate applicable?.....Is it true that if one was sitting inside the glass slab , he would see the light's speed to be 'c'? and not 2 x 10^8 m/s ? ... Is the slowing in speed of light apparent?...just because we are sitting outside it but the person inside the glass slab would see the correct light speed>??.. And suppose person A is inside the glass slab and person B is outside the slab , that is in vacuum ..and there is a light beam which goes across in the vacuum ..now what will be the light speed for person A? ...for B the light's speed will be faster outside the glass slab and slower inside the glass slab , but for person A in the glass slab , what will be the case?? and how is all of the above in accordance with the second postulate? shall i say " Light speed in glass remains same for all inertial frame observers inside glass slab" ..?