1. Light is Energy!! Mrs. Wolfe

2. Light is created when electrons jump and release energy. That makes sense, because when electrons jump, they are using kinetic energy….energy of MOTION! This energy is LIGHT! So Light energy MOVES!

3. Light Energy Moves in Waves! What is a wave? Let’s take a closer look at a wave!

4. Waves have Parts

5. Two Types of Waves Transverse Demo: Stadium wave Particles move up and down Longitudinal/Compressional Demo: Slinky Particles move side-to-side

6. Light is a Transverse Wave What type of wave is an ocean wave?

7. How does the wavelength change the wave? http://www.colorado.edu/p hysics/2000/waves_particle s/index.htmlhttp://www.colorado.edu/p hysics/2000/waves_particle s/index.html Different wavelengths have different names. List them from LONGEST wavelength to SHORTEST wavelength. ELECTROMAGNETIC Spectrum!

8. The Electromagnetic Spectrum

9. If the wavelength is LONGER, fewer waves hit you per second. If the wavelength is SHORTER, more waves hit you per second. This is called FREQUENCY. Frequency is measured in Hertz (Hz). How are frequency and wavelength related? MINI-LAB!

10. Time for a mini-lab! Go to http://www.colorado.edu/p hysics/2000/waves_particle s/lightspeed-1.html http://www.colorado.edu/p hysics/2000/waves_particle s/lightspeed-1.html How does wavelength affect frequency and the speed of a wave?

11. Which wave has a higher frequency? Longer wavelength?

12. Recall, S= D/T Speed =Wavelength x Frequency A wave has a wavelength of 2 m and a frequency of 6 Hz. Calculate the speed of the wave.

13. Practice Problem…. The wavelength of an ocean wave is 20 feet. You see two waves go by in 10 seconds. What is the speed of the wave when it hits you? (.3048 meters per foot) Wavelength: 20 ft. x.3048 m = 6.096 m 1 ft. Frequency: 2 waves/10 seconds =.2 waves per second 6.096 x.2 = 1.2 m/s

14. Frequency & Energy Draw a high frequency wave. Every time a wave hits you, it uses some energy. Would a high frequency wave have high or low energy? Which wave has the HIGHEST Energy?

15. Think back to Radioactivity! Gamma radioactive substances emit LIGHT. Think about the FREQUENCY of a gamma wave. Is this high or low energy? Why would a gamma ray hurt ? What does this energy do to your electrons?

16. Take Home Messages Two types of waves: Transverse & Longitudinal Light travels as a transverse wave. The type of light is defined by its wavelength. Wavelength, Frequency, Energy, and Speed are all related. Be able to draw a wave and label its parts. Be able to calculate wavelength, frequency, & speed