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 * 3600 s / hr * 24 frames/s = 129,600 frames

The Electromagnetic Spectrum & Types of Solar Energy

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?

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.

Visible light is an example of electromagnetic waves. So are Gamma Rays…

The Electromagnetic Spectrum

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.

The chart below shows the variation in peak wavelength emitted by an object as the temperature increases from 4500K to 7500K.

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

Do you think that it’s merely convenient that our eyes have evolved to see in the visible spectrum?

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.

How Does Radiant Energy Behave?

Electromagnetic Energy travels in waves; some waves are longer than others (i.e. some waves have different wavelengths).

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)

Reflectance (R), Absorptance (A), and Transmittance (T) are physical properties of materials.

R + T + A = 1

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!

In other words, radiant energy arriving at a surface is either reflected away, transmitted through, or absorbed by that surface.

Not all materials behave the same way at all wavelengths. For example, glass transmits visible light but reflects infrared and ultraviolet wavelengths.

Using what you’ve learned, explain why the inside of car gets hot on a sunny day?

Infrared

Types of Solar Energy

1. Passive

2. Active

Types of Solar Energy

Passive

The capture and use of solar energy w/o the aid of any moving mechanical systems.

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

What’s Coming Up?

Passive Solar Energy

Active Solar Energy

Power Transmission

Impacts on Environment/Society