Activity: Global energy transfer
In this jam-packed activity about the impact of the Sun's radiation on the Earth, you will explore the nature of EM radiation from a black body, show that power/area is proportional to the fourth power of temperature, learn to state and apply Stefan-Boltzmann and Wien's laws, describe the interaction between EM radiation and different types of matter, define surface heat capacity, emissivity and albedo, understand the greenhouse effect and (as if that wasn't enough) build an iterative simulation of the Earth-Sun system with Excel.
Need to know
Energy from the fusion of hydrogen in the core of the Sun heats the gas on the outside causing it to emit light.
Here is an animation showing the stages of the hydrogen fusion process, note how long it takes.
- Why doesn't the core emit visible light?
- Why doesn't fusion take place in the outer layers?
You have seen how light is absorbed when an atomic electron is excited from one energy level to another. This only happens for specific wavelengths so gases are quite transparent to visible light. The atmosphere consists of a mixture of gases most made of molecules rather than atoms. Carbon monoxide, nitrogen, oxygen, carbon dioxide, water, nitrogen dioxide and ozone are all molecular gases found in air. The way EM radiation interacts with these molecules can be investigated in the following simulation:
Starting with Carbon monoxide try shining different wavelengths of EM radiation at the molecules. Make a suitable table for your results. Note that a short time after absorbing the radiation the molecule returns to its non excited state, when this happens radiation is re emitted but in a random direction.
The following graphs show the % absorption of radiation by 3 different gases. Use the results from the simulation to explain them.
Here is an energy flow diagram made in GeoGebra:
- Set the values as in the previous example to see if the numbers match.
- Observe the effect of changing the variables.
Now you can build your own model in Excel follow the instructions on page 359.