Question

An iron rod is heated. The colors at different temperatures are noted. Which of the following colors shows that the iron rod is at the lowest temperature?

(a) Red

(b) Orange

(c) White

(d) Blue

The question was asked by my school teacher while I was bunking the class.

Question is taken from Black Body Radiation topic in section Quantum Physics of Engineering Physics I

Answer 1

The correct choice is (a) Red

Explanation: As the body gets hotter, the frequency of the emitted radiation keeps on increasing. Blue color has the highest frequency out of red, orange and white. Thus, as the iron rod gets heated first it would become red, then orange, then white and then finally blue.