Question

Three objects coloured black, gray and white can withstand hostile conditions upto $2800^{\circ} C$. These objects are thrown into a furnace where each of them attains a temperature of $2000^{\circ} C$. Which object will glow brightest?

• A. The white object
• B. The black object
• C. All glow with equal brightness
• D. Gray object

Answer 1

Answer: (B)

An ideal black body absorbs all the radiations incident upon it and has an emissivity equal to 1 . If a black body and an identical another body are kept at the same temperature, then the black body will radiate maximum power. Hence, the black object at a temperature of $2000^{\circ} C$ will glow brightest.