Electromagnetic spectrum:

Idea launchers:

1. Names five different kinds of waves.
2. How are all the waves the same?
3. How are the waves different?
4. Which types of radiation do you recognize in the provided spectrum?
5. Which color has the shortest wavelength (λ) according to the spectrum?
6. Why does a CD or DVD look like a rainbow of colors when you look at it?

Landing pad:

1. Did you see different things with different light sources?
2. Did you see emission or absorption spectra?
3. How was sunlight different from the discharge tubes?
4. If your shirt looks blue, what color does it absorb?
5. What color would you predict the sky to look in a forest fire area?
6. What similarity did you notice between the wavelength of the visible light and the spacing in your CD?

Rays of knowledge:

1. Light is energy that comes from the sun as a continuous spectrum. We can see how this white light separates into colors and produces a rainbow when there are small water droplets in air.
2. Lots of things can happen to light as it travels.
   • It can be transmitted — passes through something like clear glass.
   • It can be reflected — bounces back like what a mirror does.
   • It can be refracted — bent and changed like when the light goes from air to water, such as a straw in a glass looking “broken.”
   • It can be absorbed — captured by something and not returned. If your shirt looks red, it is because it absorbs green light.
   • It can be scattered — gas molecules and dust send light in every direction. Blue scatters more than other colors, so the sky looks blue. With smoke or at sunrise/sunset (longer path), red/yellow become more visible.
   • It can be diffracted — light waves bend around openings; greater wavelength gives more diffraction.
3. Different light sources give off different wavelengths of light. One way to see this is to bend light into its component wavelengths using a diffraction grating.
4. CD is made of plastic with many tiny grooves ~1.6 microns (1.6×10^-6 m) apart. As light interacts with the grooves, it is bent; longer wavelengths are bent more than shorter wavelengths.
5. Absorption spectrum looks like a dark background with light-colored lines.
6. Emission spectrum looks like a rainbow of colors with dark lines.
7. Applications Both emission and absorption spectra are like fingerprints for elements. Even for distant stars, composition can be inferred from their spectra — this is how helium was discovered.