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PHY 299 Spring 2009 Bob Brecha

Radiation – Electromagnetic Energy

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Radiation – Electromagnetic Energy. PHY 299 Spring 2009 Bob Brecha. Light Waves. Light is a form of wave, like a water wave or a wave on a rope. But ... waves need something to “wave” ( e.g. water or rope or a crowd ) Light (electromagnetic) waves can also move through vacuum. - PowerPoint PPT Presentation

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Page 1: Radiation – Electromagnetic Energy

PHY 299 Spring 2009Bob Brecha

Page 2: Radiation – Electromagnetic Energy

Light is a form of wave, like a water wave or a wave on a rope. But ...waves need something to “wave”(e.g. water or rope or a crowd)

Light (electromagnetic) waves can also move through vacuum.

Page 3: Radiation – Electromagnetic Energy

Light waves are reallymade up of electric fields and magnetic fields - more on that later

Moving electric charges are the source for all electromagnetic waves.

Page 4: Radiation – Electromagnetic Energy

wavelength

Page 5: Radiation – Electromagnetic Energy

T

T period

Page 6: Radiation – Electromagnetic Energy

The period of a wave is related to the wavelength of the wave. It is sometimes easier to talk about the “frequency” of the wave rather than the period

f = 1/T c = f ×

c = speed of light (300,000 km/sec.)

Page 7: Radiation – Electromagnetic Energy

0.00E+00

5.00E-02

1.00E-01

1.50E-01

2.00E-01

2.50E-01

3.00E-01

3.50E-01

4.00E-01

4.50E-01

0.00E+00

1.00E-05

2.00E-05

3.00E-05

4.00E-05

5.00E-05

6.00E-05

7.00E-05

8.00E-05

Ra

dia

tio

n in

ten

sit

y

Wavelength

Blackbody radiation (300 K)

Page 8: Radiation – Electromagnetic Energy

Low temperaturesLong wavelength radiation40ºC 10,000 nm peak (10 m)

High temperatures Shorter wavelength radiation6000 ºC 500 nm peak (0.5 m)

0.00E+00

5.00E-02

1.00E-01

1.50E-01

2.00E-01

2.50E-01

3.00E-01

3.50E-01

4.00E-01

4.50E-01

0.00E+00

1.00E-05

2.00E-05

3.00E-05

4.00E-05

5.00E-05

6.00E-05

7.00E-05

8.00E-05

Radi

atio

n in

tens

ity

Wavelength

Blackbody radiation (300 K)

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