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118/02/09 Habbal_Astro110-01 Lecture 13
Astro110-01 Lecture 13Light: The Cosmic Messenger
[Chapter 5 in The Essential Cosmic Perspective]
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218/02/09 Habbal_Astro110-01 Lecture 13
Basic Properties of Light and Matter
Our goals for learning:• What is light?• What is matter?• How do light and matter interact?
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318/02/09 Habbal_Astro110-01 Lecture 13
Discovering the components of light
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418/02/09 Habbal_Astro110-01 Lecture 13
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518/02/09 Habbal_Astro110-01 Lecture 13
Light is an electromagneticwave
Properties of awave:- Wavelength- Frequency- Speed
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618/02/09 Habbal_Astro110-01 Lecture 13
Wavelength, Frequency and Speed
wavelength × frequency = speed of wavespeed of light wave = constant = 3 108 m/s
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718/02/09 Habbal_Astro110-01 Lecture 13
The Electromagnetic Spectrum
Inverse relationship between wavelength and frequency
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818/02/09 Habbal_Astro110-01 Lecture 13
Particles of Light
• Particles of light are called photons.• Each photon has a wavelength and a
frequency.• The energy of a photon depends on its
frequency.
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918/02/09 Habbal_Astro110-01 Lecture 13
Wavelength, Frequency, andEnergy λ × f = c
λ : wavelength f : frequency
c: speed of light = 3.00 × 108 m/s
photon energy: E = h × fPlanck’s constant: h = 6.626 × 10−34 joule⋅s
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1018/02/09 Habbal_Astro110-01 Lecture 13
Thought Question
The higher the photon energy,• the longer its wavelength.• the shorter its wavelength.• Energy is independent of wavelength.
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1118/02/09 Habbal_Astro110-01 Lecture 13
Thought Question
The higher the photon energy,• the longer its wavelength.• the shorter its wavelength• Energy is independent of wavelength.