1. 1. A Light Wave What is light? What is color? What does the word “frequency” mean?

2. 1. A Light Wave OBJECTIVE: To understand what light and colors are

3. 1. A Light Wave Light is a WAVE This wave has electrical properties AND This wave has magnetic properties So we call light an electro-magnetic wave

4. 1. A Light Wave Spectrum = a range This picture is a range of waves from long to short

5. 1. A Light Wave

6. 1. A light wave WavelengthFrequency What is it Symbol: Unit: 2 quantitative properties of a wave

7. 1. A Light Wave Wavelength: distance between two waves “crest to crest” or “trough to trough”

8. 1. A Light Wave What does it mean to do something frequently?

9. 1. Quantum Model Frequency: how many waves in 1 second

10. 1. Quantum Model 2 properties of waves Wavelength: distance between two waves either crests or troughs Symbol: l Units = meters, m

11. 1. Quantum Model 2 properties of waves Frequency: How many waves in 1 second Symbol: v Units = Hz, or sec -1

12. 1. Quantum Model

13. Which has a longer wavelength: radio or ultraviolet?

14. 1. Quantum Model Which has a higher frequency: radio or ultraviolet?

15. 1. A Light Wave Heat energy in the form of Infrared waves

16. 1. A Light Wave X-RaySunburn from UV rays

17. 1. Quantum Model 2 properties of waves Wavelength: is… Symbol: ? Units = ? Frequency: is… Symbol: ? Units = ? What does it mean for wavelength and frequency to have an inverse relationship?

18. 1. Quantum Model 2 properties of waves l = Wavelength v = Frequency C = Speed of light = 3.0 x 10 8 meters/seconds <- this number never changes l v = c l

19. 1. Quantum Model Calculations using l v = c Your favorite radio station broadcasts the signal at 99.5 MHz. This is equal to 9.96 x 10 7 Hz. Calculate the wavelength in meters. 1. Write the equation: l v = c 2. Plug in values. C = 3.0 x 10 8 m/s ALWAYS 3. Rearrange equation to solve for unknown. 4. Solve Answer = 3.01 meters

20. 1. Quantum Model Calculations using l v = c Photosynthesis uses light waves with a wavelength of 660 nm to convert CO 2 and H 2 O into glucose and O 2. 660 nm = 6.6 x 10 - 7 m. Calculate the frequency. 1. Write the equation: l v = c 2. Plug in values. C = 3.0 x 10 8 m/s ALWAYS 3. Rearrange equation to solve for unknown. 4. Solve Answer = 4.5 x 10 14 Hz or 4.5 x 10 14 sec -1

21. 1. A Light Wave Answer on Warmup Paper. Label it as “WAVES” Your favorite FM radio station broadcasts at a frequency of 101.1 MHz. This is equal to 1.011 x 10 8 Hz. What is the wavelength of this station in meters? A police officer is using a radar gun for speeding citations. The gun uses waves with a wavelength of 8.45 nanometers. This is equal to 8.45 x 10 -9 meters. What is the frequency in Hz?

22. 1.Make sure that l is in METERS, or that v is in Hz 2.If not, then convert to METERS or Hz using the conversion factors given to you. 3.Solve: Step-by-step instructions on how to solve should be in your notes 4.Does your final answer have the units that is asked for in the problem?

23. 1. A Light Wave 1. What is light? 2. What are the symbols and units for the two quantitative properties of a wave? 3. What is the relationship between the two quantitative properties? 4. Explain why we have different colors using the two quantitative properties 5. What does a high frequency mean in terms of energy? Summary & Review