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Heat Transfer

A series of free Online High School Physics Video Lessons.



In this lesson, we will learn

  • radiant energy
  • Newton's Law of Cooling
  • how the greenhouse effect works

Radiant Energy

Radiant Energy is a type of thermal energy transfer involving electromagnetic waves. In the case of visible light, radiant energy is visible to the human eye, but in all other cases, it is not.

Understanding the concept of radiant energy

Law of Cooling

Newton's law of cooling states that a hot object will transfer its heat to a cooler object faster depending on how cold that object is. Stated mathematically, it says that the rate of change of the hot object is proportional to the temperature difference between it and its surroundings.

Understanding and applying the law of cooling.
How to find a time a certain temperature occurs at and also how to calculate a rate of temperature change.
Newton's Law of Cooling (for an increase in temperature)




Greenhouse Effect

In the greenhouse effect, the gases of which our atmosphere is composed absorbs the thermal energy that the Earth radiates and reflects some of it downwards again, towards the Earth, effectively trapping heat inside the atmosphere. As light arrives from the sun, more and more thermal energy is trapped, increasing the temperature of the planet.

The temperature of earth has been relatively constant over time. This is possible because as the planet absorbs solar radiation, it also emits longwave radiation into space. Despite this radiative equilibrium, some longwave radiation remains trapped beneath the atmosphere of the earth and warms the surface of the earth. This phenomenon is called the "greenhouse effect."

How the greenhouse effect works?
Green house Effect and Global warming


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