Question

You place three nonflammable objects in a fire. They are identical in shape and size, but one object is black, the second is white, and the third is shiny silver. After a few minutes, all three objects are at the same temperature: 1800° C. They remain solid and are now glowing with thermal radiation. Which one is glowing most brightly? The first object (black). They are all glowing with equal brightness. The third object (silver). The second object (white).

Answer 1

Answer:

The first object (black)

Explanation:

The thermal radiation of a body is governed by the Stefan Boltzmann Law, which is mathematically given as:

$E=\epsilon. \sigma.T^4$

where:

$\sigma =5.67\times 10^{-8}\ W.m^{-2}.K^{-4}$      (Stefan Boltzmann constant)

• Also the absorptivity and emissivity of a perfectly black body is maximum ( =1 ) therefore it absorbs all the heat energy incident on it and glows the brightest due to the perfect emission.

So here also the black object will glow brighter than the others.