Perhaps the highest temperature material you will ever see is the sun's outer atmosphere, or corona. At a temperature of about `2 times 10^(6@)C " or " 3.6 times 10^(6@)F`, the corona glows with a light that is literally unearthly. But because corona is also very thin, its light is rather faint. You can only see the corona during a total solar eclipse when the sun's disk is covered by the moon.
To measure high temperatures `> 2500^(@)C` we use

Options

A. constant volume gas thermometer
B. thermocouple
C. resistance thermometer
D. pyrometer

Answer

D