1. Do Now:
How many frames are in a Pixar animated movie such as The Incredibles? [What would you need to know? Explain your reasoning and show your work.]
Avg. Length * Seconds/Hour * Frames/Second = # of Frames
1. 5 hours * s / hr * 24 frames/s = 129,600 frames

2. The Electromagnetic Spectrum & Types of Solar Energy

3. Essential Questions
What is the electromagnetic spectrum, how does it behave, and how is it related to temperature?
What is active solar energy and how can it be used?
What is passive solar energy and how can it be used?

4. The Electromagnetic Spectrum
The star at the center of our planetary system, our sun, is named Sol. That’s why our system is called the Solar system.
Our sun averages about 5800K in temperature and emits energy in the form of electromagnetic waves.
The distance between peaks in an electromagnetic wave is called the wavelength. Different wavelengths of electromagnetic radiation are released at different temperatures.
So are Gamma Rays…
Visible light is an example of electromagnetic waves.

5. The Electromagnetic Spectrum
The chart below shows the variation in peak wavelength emitted by an object as the temperature increases from 4500K to 7500K.
Have you noticed that filament light bulbs, radiant heaters, and ceramic stovetops all seem to glow as they heat up? You will notice their color change from red, to orange, to yellow as they get hotter…emitting all colors of the visible spectrum, the hotter they get.
Do you think that it’s merely convenient that our eyes have evolved to see in the visible spectrum?
Do you remember the average temperature of our sun? What would its peak wavelength be? What color of light would be brightest?
Sol is approximately 5800K
Green light is the peak wavelength

6. The Visible Spectrum What is the Visible Spectrum?
The visible spectrum is that part of the electromagnetic spectrum that is visible to the human eye…from about 390 nm to 750 nm.
Much of the energy from our sun is emitted in the visible range. There are also significant amounts in the infrared and ultraviolet ranges as well.
All of this energy travels as waves and behaves according to certain physical principles.

7. How Does the Color/Wavelength of Light Affect PV Efficiency?
Test 5-8 colors using different backgrounds on PowerPoint Slides
Purple
Blue
Green
Yellow
Orange
Red
White

8. Approximate Wavelength: 390-455 nanometers

9. Approximate Wavelength: 455-492 nanometers

10. Approximate Wavelength: 492-577 nanometers

11. Approximate Wavelength: 577-597 nanometers

12. Approximate Wavelength: 597-622 nanometers

13. Approximate Wavelength: 622-780 nanometers

14. How Does Radiant Energy Behave?
Electromagnetic Energy travels in waves; some waves are longer than others (i.e. some waves have different wavelengths).
Infrared
Blue light has shorter waves than the rest of the visible spectrum, so it is scattered more by molecules in the atmosphere. That is why our sky appears blue!
Reflectance (R), Absorptance (A), and Transmittance (T) are physical properties of materials.
R + T + A = 1
Using what you’ve learned, explain why the inside of car gets hot on a sunny day?
Not all materials behave the same way at all wavelengths. For example, glass transmits visible light but reflects infrared and ultraviolet wavelengths.
The inside of a car gets hot because not all of the visible light that passes through the glass gets reflected back out; some of that energy is absorbed by the car’s interior which heats up and then begins emitting in the infrared. But since infrared rays are reflected by the glass, they are trapped inside and the heat energy inside the car builds and builds!
Waves travel in straight lines unless interrupted; then they can be…
Reflected (like with a mirror)
Absorbed (like with asphalt on a hot day)
Transmitted (bent, but allowed to pass through, like with water or a prism)
In other words, radiant energy arriving at a surface is either reflected away, transmitted through, or absorbed by that surface.

15. Types of Solar Energy
Passive
Active

16. Types of Solar Energy
Passive
The capture and use of solar energy w/o the aid of any moving mechanical systems.

17. Types of Solar Energy
Active
The capture and use of solar energy and its conversion to heat or electricity using mechanical or chemical systems or effects

18. What’s Coming Up? Passive Solar Energy Active Solar Energy
Power Transmission
Impacts on Environment/Society