Filament Surface Temperature

[sheikhfahad]

i am an A-Level student second year and i got this partical exam, i want some help.

i wanted to know how to measure the temperature of the sureface of the lamp. What thermometer would be the best to measure the temperature and why? thank you

[Integral]

A filament is a blackbody radiator its color is a direct indication of its temperature. The instrument used for this purpose is Called and Optical pyrometer. You view the filament through an eyepiece while adjusting an internal filament to match the color of the filament to be measured. The temperature is then read from a dial. Any thermometer or direct contact measurement would have such a large effect on the temperature of the filament that any reading obtained would be meaningless. The only way to get a meaningful temperature is be color comparison.