1. Electrons in Atoms
Chapter 4

2. Electromagnetic Spectrum
All waves move at speed of light, c, 3.00x108 m/s
Waves identified by:
wavelength, , the distance b/ corresponding points on adjacent waves. Units: nm, cm, or m
Frequency, , # of waves that pass a given point in a specific time, 1 sec. Unit: 1/s = Hertz, Hz

3. Frequency ()
Measured in cycles/second = hertz (Hz)

4. Wavelength and Frequency
Inverse proportion equation!!
Frequency, 1/s
speed of light, m/s
wavelength, m

6. A photon of red light has a wavelength of 665 nm
A photon of red light has a wavelength of 665 nm. What is the frequency of this light?
665 nm = 665 x 10-9 m
c =  • 
 = c ÷  = 3.00 x 108 m/s ÷ 665 x 10-9 m
 = x 1014/s or Hz
 = 4.51 x 1014/s or Hz

7. An x-ray has a frequency of 7.25 x 1020 Hz. What is the wavelength?
7.25 x 1020 Hz = 7.25 x 1020/s
c =  • 
 = c ÷  = 3.00 x 108 m/s ÷ 7.25 x 1020/s
 = x m
 = 4.14 x m

8. Energy of Electromagnetic Radiation
For all waves: E = h • 
h = 6.63 x J • s or J/Hz 8

9. A photon of red light has a wavelength of 665 nm
A photon of red light has a wavelength of 665 nm. What is the energy of this light?
665 nm = 665 x 10-9 m
c =  • 
 = c ÷  = 3.00 x 108 m/s ÷ 665 x 10-9 m
 = x 1014/s or Hz
 = 4.51 x 1014/s or Hz

10. Electromagnetic Spectrum
What is the color of an electromagnetic radiation with an energy of 3.4 x10-19 J?