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Today’s Topics

• Quantum Theory

• Wave Properties

• The Electromagnetic Spectrum

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.

Waves

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.

Parts of the Wave

Wavelength () – Distance between identical points on successive waves.

Frequency() – 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.

REMEMBER THIS IMPORTANT FORMULA

Wave velocity = Wavelength x Frequency

u = Speed = distance/time

(m/s)

Wavelength = distance between waves (nm)

Frequency = waves/time (s-1, 1/s, Hz)

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

ELECTROMAGNETIC SPECTRUM

Shows difference in wavelength and frequency for different types of

electromagnetic radiation.

Electromagnetic Radiation

Review

• Wave

• Wavelength

• Frequency

• Amplitude

• Electromagnetic Radiation

How do you cook a meal in 3 minutes?

Use a microwave ovenMicrowave – electromagnetic radiation, which is a

type of wave.Wave – Vibrating disturbance by which energy is

transmitted.Microwave frequency = 2500 MHz or 2.5 GHzThis 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!