Review the key concepts, formulae, and examples before starting your quiz.
🔑Concepts
Radiation is the mode of heat transfer that does not require any material medium like solid, liquid, or gas.
Heat from the Sun reaches the Earth through the vacuum of space primarily by the process of radiation.
Every hot object, whether solid, liquid, or gas, emits heat radiation in all directions.
When radiant heat falls on an object, a part of it is absorbed, a part is reflected, and a part may be transmitted. The temperature of the object increases due to the absorbed part of the heat.
Dark-colored surfaces are better absorbers and better radiators of heat than light-colored or shiny surfaces.
In summers, we prefer light-colored clothes because they reflect most of the heat that falls on them, keeping us cool. In winters, we wear dark-colored clothes as they absorb more heat from the surroundings.
The temperature of a body is often measured in degrees Celsius () or Kelvin ().
📐Formulae
💡Examples
Problem 1:
Suppose you have two identical metal containers, one painted black and the other painted white. If both are filled with water at and left in a room at , which one will cool down faster?
Solution:
The container painted black will cool down faster.
Explanation:
Dark-colored surfaces are better radiators of heat than light-colored surfaces. Since the black container is a better radiator, it will lose heat to the surroundings more quickly through radiation, leading to a faster drop in temperature.
Problem 2:
Calculate the difference in temperature between two bodies if Body A is at and Body B is at .
Solution:
Explanation:
To find the temperature difference, we subtract the lower temperature from the higher temperature using simple subtraction: