1. Waves Chemistry Mrs. Coyle

2. Wave Wave: a rythmic disturbance in both time and space.
Waves transfer energy not matter.

3. Amplitude: The distance from the equilibrium (baseline) to the crest or trough)

4. Wavelength: The distance from the crest to crest or trough to trough.

5. Frequency: the number of waves per second (Hertz, Hz)l

6. Low amplitude - High amplitude

7. Speed of a Wave
v =lf
v speed
l wavelength
f frequency

8. Speed of a Wave
v= d/t v = l/T v =lf

9. Transverse Waves
The particles vibrate perpendicular to the direction of the wave's propagation
(ex: waves along a string, electromagnetic waves).

10. Longitudinal Waves
The particle displacement is parallel to the direction of wave propagation (ex: sound)

11. Elliptical Waves
Result when longitudinal and transverse waves are superpositioned.
(ex: surface water waves)

12. Torsional Waves http://www.youtube.com/watch?v=P0Fi1VcbpAI
Video link on Web

13. Wave Categories Mechanical Waves: require a medium.
Examples:
Water waves( Tsunami)
Sound waves (f= hertz, v= 340 m/sec in air but varies for different media, faster in solids)
Earthquake waves
Electromagnetic Waves: do not require a medium. Can travel through space (vacuum).
Example: Light from the sun reaches us
Note: all EM waves have a speed through vacuum of 3 x 108 m/sec.

14. Electromagnetic Waves
Type of radiation Wavelengths(m)
Radio TV
Microwave
Infrared radiation
visible light
red 700x (700nm)
orange
yellow
green
blue
indigo
violet 400x (400nm)
ultraviolet
x-rays
gamma rays shorter than 10-12

17. Note
A wave’s speed is constant in a given medium. If you change the frequency of the wave, the wavelength will also change. If the frequency increases, the wavelength will decrease.
When a wave travels from one medium to a different medium, the frequency remains the same and the speed changes.

18. Problem
What is the frequency of a light wave of wave length 550x 10-9 m?
What color light is it?

19. Refraction

20. Dispersion

21. Diffraction

22. Remember my atomic model?

23. Niels Bohr’s Atomic Model (1913)
Electrons orbit the nucleus in circular paths of fixed energy (energy levels).

24. Niels Bohr’s Atom Cont’d
Electrons can jump from energy level to energy level.
Electrons absorb or emit light energy when they jump from one energy level to another.

25. Hydrogen Emission Spectrum
Violet 410nm
Blue nm
Blue-Green 486 nm
Red nm
Balmer Series

26. Bohr Model for Hydrogen