1. Light and Quantized Energy

2. Electromagnetic Radiation
Electromagnetic radiation: A form of energy that exhibits wavelike behavior as it travels through space
Light: a form of electromagnetic radiation

3. What are some examples of electromagnetic radiation?
What else?

4. Electromagnetic Radiation
Waves have a frequency
Use the Greek letter “nu”, , for frequency, and units are “cycles per sec”
 stand for wavelength – it’s the shortest distance between equivalent points on a continuous wave
All radiation: c =  •  where c = velocity of light = 3.00 x 108 m/sec

5. Electromagnetic Radiation
wavelength
Visible light
Ultaviolet radiation
Amplitude
Node
Crest

6. Electromagnetic Spectrum
In increasing energy, ROY G BIV

7. Electromagnetic Spectrum
Long wavelength --> small frequency
Short wavelength --> high frequency
increasing frequency
increasing wavelength

8. Practice Problems
What is the frequency of green light, which has a wavelength of 4.90 x 10-7m?
What is the speed of an electromagnetic wave that has a frequency of 7.8 x 106 Hz?

9. Quantum Concept
1900 German physicist Max Planck started to search for WHY light emitted from heated objects.
Found that QUANTUM is the minimum amount of energy that can be gained or lost by an atom
Matter can gain or lose energy in small specific amounts called quanta

10. Quantum Concept
Planck showed mathematically that the energy of a quantum is related to the frequency of the emitted radiation.
Equantum = hn
E = energy
h = Planck’s constant = x J·s
n = frequency

11. Photoelectric Concept
Photoelectric effect: photons are emitted from a metal’s surface when light of a certain frequency shines on a surface
Albert Einstein proposed that electromagnetic radiation has both wavelike and particlelike natures. He calculated that the photon energy was:
Ephoton = hn

12. Electromagnetic radiation.

13. “Ground State” – lowest energy state
“Excited State” – Electrons jump to higher energy levels due to an input of energy
Absorption – amount of E absorbed to “boost” e- to higher E level (excited state)
Emission – e- releasing E when “falling” back to lower E level (ground state)

15. Bohr model Studying H atom emission spectrum lead to Bohr’s model –
electrons are restricted to certain orbits corresponding to E levels
Rutherford never explained
how e- fill space surrounding
the nucleus

16. Practice Problems
What is the energy for each of the following types of radiation?
a x 1020 s-1
b x 1013 Hz
c x 1016 s-1