Considering Influences and Implications of Light and Thermal Phenomena on World Climate

So far, we have been describing the direction that the light rays travel using straight lines like particles (photons). We are shifting our thinking about light rays and are beginning to discuss the idea of light traveling in a wavy line (still moving in a straight direction). In this model, visible light is part of the electromagnetic spectrum (red, orange, yellow, green, blue, indigo, violet). The electromagnetic spectrum also includes bigger and smaller waves, and Emily asked the students to consider other types waves they had heard of. The students shared their ideas with a partner, and came up with UV rays, and microwaves. With some more questioning, they were also able to come up with radio waves, cell phone waves (also radio waves).
I asked the students if they had heard of something called infra red radiation and a few raised their hands. They reported knowing that cameras can be used in the dark to see people using their body heat. Emily showed the students a couple of clips which used infra red cameras to show body heat and warm water in a glass.


New Terms:

• Emissivity: hot objects emit energy called “infrared radiation” which is part of the electromagnetic spectrum.
  
• Greenhouse Effect: when sunlight can shine on earth (visible spectrum includes red, orange, yellow, green, blue, violet) and be absorbed and re-emitted as infrared radiation. If there are clouds, some of the infrared light does not escape into space but is reflected back to Earth. This warms the earth. Emily asked the students what they have experienced happening in their car when they leave it sitting in the sun for a long period of time without any windows open. Many replied with the same thing: it gets really hot. She used a relatable experience to help the students understand the greenhouse effect more easily.
  
• Conduction: hot object is in contact with a cooler object– transfer of energy from the hot object by heating the cooler object (example: bottom of a pan on a stove burner).
  
• Convection: transfer of energy from one place to another by movement of fluids; the more dense fluid will sink while the less dense fluid rises.
  

The class modeled an effect of the warming earth by comparing what happens when ice that is already in water melts and when ice that is on land melts: