The active element of a certain laser is made of a glass rod 30cm long and 1.5cm in diameter. The average coefficient of linear expansion of glass is 9 x 10^-6°C-1. If the temperature of the rod increases by 65°C, what is the increase in its volume?

Answer 1

Ok, most important is the change in length in a laser, but volume will be

coeffVolumeExpansion=appx 3*coeffLinearExpansion.

See the section isotropic materials:
http://en.wikipedia.org/wiki/Thermal_expansion