1. Electromagnetic Spectrum

2. Light
Is light a wave or a particle?
Light is BOTH!

3. Electrons
Excited state: a state in which an electron has absorbed energy and moved into a higher energy level
Ground state: the normal energy level an electron exists in according to its electron configuration

4. Energy absorbed by the electron to make it EXCITED !!!
Energy lost by the electron to return to its Ground state 

5. Frequency
*** Look at the example below what happens to the wavelength as the frequency increases?
IMPORTANT: As the frequency increases, the wavelength decreases
As the wavelength increases, the frequency decreases
2 cycles per second
4 cycles per second
8 cycles per second
1 second

6. Relationship of frequency, wavelength, and energy with light waves

7. Formulas Conversions 1 nm = 1 x 10-9 m c = ln 1 Angstrom = 1 x 10-10 m
λ = wavelength (meters)
n = frequency (Hz or sec-1)
c = speed of light = 3 x 108 m/s

8. Practice Problem #1
What is the wavelength of light with a frequency of 6.75 x 1014 Hz?

9. Practice Problem #2
 What is the wavelength (in nm) of EMR with a frequency of 4.95 x 1014 s¯1?

10. Practice Problem #3
 What is the frequency of EMR having a wavelength of 555 nm? (EMR is an abbreviation for electromagnetic radiation.)

11. Practice Problem #4
What is the frequency of red light having a wavelength of 7000 Angstroms?

12. Formulas Energy(photon) = hc λ
h = Planck’s constant = x J x s
c = speed of light
λ = wavelength (meters)
E = hn
h = Planck’s constant = x J x s
n = frequency (Hz or sec-1)

13. Practice Problem #1
A sodium vapor lamp emits light photons with a wavelength of 579 nm. What is the energy of these photons?

14. Practice Problem #2
Find the energy for an x-ray photon with a frequency of 2.4 × 1018 Hz.

15. Practice Problem #3
What is the frequency of UV light that has an energy of 2.39 × J?

16. Practice Problem #4
If a laser emits 2.3 x J/photon, what is the wavelength of this light?