- Quantum theory proposes that atoms and molecules emit and absorb energy in discrete quantities called quanta, challenging the classical view that they behave like balls. - There are two types of waves: longitudinal waves where particle displacement is parallel to propagation, and transverse waves where displacement is perpendicular. - The electromagnetic spectrum shows the difference in wavelength and frequency for different types of electromagnetic radiation, from radio waves to gamma rays. Microwaves use electromagnetic radiation at a frequency of 2.5 GHz to heat food by being readily absorbed by water.

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2. Today’s Topics
• Quantum Theory
• Wave Properties
• The Electromagnetic Spectrum

3. History of Quantum Theory
• Classic Mechanics:
– Molecules behave like balls
• Pro – Explained things like pressure
• Con – Did not explain molecule well
• Quantum Theory
– Maxwell Planck (1858 – 1947)
• Discovered that atoms & molecules emit / absorb
energy only in certain discrete quantities called
quanta.

4. Waves

5. Not those waves, these waves
Wave – a vibrating
disturbance by which
energy is transferred
2 Types of Waves:
1)Longitudinal – particle
displacement is parallel
to direction of wave
propagation
2)Transverse – particle
displacement is
perpendicular to the
direction of wave
propagation.

6. Parts of the Wave
Wavelength (λ) – Distance
between identical points
on successive waves.
Frequency(ν) – The number
of waves that pass
through a particular point
in 1 second.
Amplitude – Vertical
distance from the midline
of a wave to the peak or
trough.

7. REMEMBER THIS
IMPORTANT FORMULA
Wave velocity = Wavelength x Frequency
u = λν
Speed = distance/time (m/s)
Wavelength = distance between waves (nm)
Frequency = waves/time (s-1
, 1/s, Hz)

8. James Maxwell
1873 – Proposed that light is an electromagnetic wave.
Electromagnetic wave – Has an electric field component
and a magnetic field component with the same
wavelength and frequency, but travels in perpendicular
planes.
Electromagnetic Radiation – emission and transmission of
energy in the form of electromagnetic waves.
Electromagnetic waves travel at 3.00x108
m/s in a vacuum.
The speed of light (c) = 3.00x108
m/s

9. ELECTROMAGNETIC SPECTRUM
Shows difference in wavelength and
frequency for different types of
electromagnetic radiation.

10. Electromagnetic Radiation

11. Review
• Wave
• Wavelength
• Frequency
• Amplitude
• Electromagnetic Radiation

12. How do you cook a meal in 3 minutes?
Use a microwave oven
Microwave – electromagnetic radiation, which is a
type of wave.
Wave – Vibrating disturbance by which energy is
transmitted.
Microwave frequency = 2500 MHz or 2.5 GHz
This frequency is readily absorbed by water, but not
plastic or glass. The absorbed energy is then
converted to atomic motion, which we all know
is heat!