Temperature Dependence of the Refractive Index of Flint Glass

The variation of the refractive index of a material with the frequency of light, n = f(ν) shows the optical response of that material. We study changes in n for flint glass to radiation when the interaction between light and glass is assisted by background energy. One way is by changing the environmental temperature, T. For a system in thermal equilibrium, such change adds kT average energy, where k is the Boltzmann constant. This energy goes into the vibration of the glass electric dipoles, hv. For an isotropic increase in kT energy, the glass dipoles change their vibrational energy according to hv' = hv + kT. In practice, we can add kT energy from a hot source (i.e. a flare) or using a blackbody radiation source placed near the glass. However, the efficiency is very small due to strong energy dissipation inside the glass. A more efficient way to change the energy is by supplying an isotropic energy across the glass. For this goal, we set up a capacitor configuration which has a glass placed between two conducting plates. In this way, changing the voltage, V, changes the frequency, v, of the vibratory dipoles as hv' = hv + eV, which is equivalent to a change in the temperature by kT. We assess the changes in n by measuring changes in the Cauchy parameter for V < 10volts. Thus, for no voltage, we get C of 11180, which increases to 11224 at 5 volts, and 11278 at 10 volts, where the error bar stays at 0.5% in all cases. These values are clear proof of the temperature variation for index n. We acknowledge The Office of Undergraduate Research – SURF program and TEAM-UP grant for funding this research.