When light goes from one material into another material having a higher index of refraction, what happens to the speed of light?

Agas expands from an initial volume of 0.040 m^3 and an initial pressure of 210 kpa to a final volume of 0.065 m^3 while its temperature is kept constant. how much work is done by the system?

Can anybody me with this? ? (picture included.)

Matter that emits no light at any wavelength is called