Martin D. Weinberg UMass Astronomy...
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Read: Chap 5 09/25/12 – slide 1 A100–Exploring the Universe: Light! Martin D. Weinberg UMass Astronomy [email protected] September 25, 2012
Transcript of Martin D. Weinberg UMass Astronomy...
Read: Chap 5 09/25/12 – slide 1
A100–Exploring the Universe: Light!
Martin D. Weinberg
UMass Astronomy
September 25, 2012
Announcements
⊲ Announcements
Orbits: summary
Tides
Experience
Interaction
Reflect/Scatter
Light/Matter
Thought question
Why Study Light?
Light as particles
Light as particles
Speed of light
Light as waves
Wave propagation
EM Radiation
Infrared
Energy & Intensity
Summary
Intensity
Thought question
What is the structureof matter?
Atomic terminology
Phases & Pressure
Internal energy
Read: Chap 5 09/25/12 – slide 2
MasteringAstronomy tutorials
⊲ You must click the “S” button to save your work
before clicking “Submit”
⊲ Animations and exercises are 50% each
⊲ Check system requirements!
Announcements
⊲ Announcements
Orbits: summary
Tides
Experience
Interaction
Reflect/Scatter
Light/Matter
Thought question
Why Study Light?
Light as particles
Light as particles
Speed of light
Light as waves
Wave propagation
EM Radiation
Infrared
Energy & Intensity
Summary
Intensity
Thought question
What is the structureof matter?
Atomic terminology
Phases & Pressure
Internal energy
Read: Chap 5 09/25/12 – slide 2
MasteringAstronomy tutorials
⊲ You must click the “S” button to save your work
before clicking “Submit”
⊲ Animations and exercises are 50% each
⊲ Check system requirements!
Today: finish Gravity & Orbits
Today: Light and Electromagnetism (LIGHT, Chap. 5)
⊲ How do we experience light?
⊲ How do light and matter interact?
⊲ What is light? What are its properties?
⊲ What is the structure of matter?
Announcements
⊲ Announcements
Orbits: summary
Tides
Experience
Interaction
Reflect/Scatter
Light/Matter
Thought question
Why Study Light?
Light as particles
Light as particles
Speed of light
Light as waves
Wave propagation
EM Radiation
Infrared
Energy & Intensity
Summary
Intensity
Thought question
What is the structureof matter?
Atomic terminology
Phases & Pressure
Internal energy
Read: Chap 5 09/25/12 – slide 2
MasteringAstronomy tutorials
⊲ You must click the “S” button to save your work
before clicking “Submit”
⊲ Animations and exercises are 50% each
⊲ Check system requirements!
Today: finish Gravity & Orbits
Today: Light and Electromagnetism (LIGHT, Chap. 5)
⊲ How do we experience light?
⊲ How do light and matter interact?
⊲ What is light? What are its properties?
⊲ What is the structure of matter?
Questions?
Gravity and Orbits
⊲ Announcements
Orbits: summary
Tides
Experience
Interaction
Reflect/Scatter
Light/Matter
Thought question
Why Study Light?
Light as particles
Light as particles
Speed of light
Light as waves
Wave propagation
EM Radiation
Infrared
Energy & Intensity
Summary
Intensity
Thought question
What is the structureof matter?
Atomic terminology
Phases & Pressure
Internal energy
Read: Chap 5 09/25/12 – slide 3
Summary
Planets obey the same laws as objects on Earth
Gravity and Orbits
⊲ Announcements
Orbits: summary
Tides
Experience
Interaction
Reflect/Scatter
Light/Matter
Thought question
Why Study Light?
Light as particles
Light as particles
Speed of light
Light as waves
Wave propagation
EM Radiation
Infrared
Energy & Intensity
Summary
Intensity
Thought question
What is the structureof matter?
Atomic terminology
Phases & Pressure
Internal energy
Read: Chap 5 09/25/12 – slide 3
Summary
Planets obey the same laws as objects on Earth
Kepler’s laws: explained by force of gravity
⊲ Planets orbit around the center of mass of the Solar
System
⊲ Since most of the mass is the Sun, Sun is very close
to center of mass
⊲ Third law depends on the sum of the two masses:
P 2 =
[
4π2
G(m1 +m2)
]
a3
Gravity and Orbits
⊲ Announcements
Orbits: summary
Tides
Experience
Interaction
Reflect/Scatter
Light/Matter
Thought question
Why Study Light?
Light as particles
Light as particles
Speed of light
Light as waves
Wave propagation
EM Radiation
Infrared
Energy & Intensity
Summary
Intensity
Thought question
What is the structureof matter?
Atomic terminology
Phases & Pressure
Internal energy
Read: Chap 5 09/25/12 – slide 3
Summary
Planets obey the same laws as objects on Earth
Kepler’s laws: explained by force of gravity
⊲ Planets orbit around the center of mass of the Solar
System
⊲ Since most of the mass is the Sun, Sun is very close
to center of mass
⊲ Third law depends on the sum of the two masses:
P 2 =
[
4π2
G(m1 +m2)
]
a3
New types of unbound orbits — hyperbolas and
parabolas — in addition to ellipses
Orbits revisited
Announcements
⊲ Orbits: summary
Tides
Experience
Interaction
Reflect/Scatter
Light/Matter
Thought question
Why Study Light?
Light as particles
Light as particles
Speed of light
Light as waves
Wave propagation
EM Radiation
Infrared
Energy & Intensity
Summary
Intensity
Thought question
What is the structureof matter?
Atomic terminology
Phases & Pressure
Internal energy
Read: Chap 5 09/25/12 – slide 4
How do gravity and energy together allow usto understand orbits?
Total orbital energy (gravitational + kinetic) stays
constant if there is no external force
Orbits cannot change spontaneously.
Changing an orbit
Announcements
⊲ Orbits: summary
Tides
Experience
Interaction
Reflect/Scatter
Light/Matter
Thought question
Why Study Light?
Light as particles
Light as particles
Speed of light
Light as waves
Wave propagation
EM Radiation
Infrared
Energy & Intensity
Summary
Intensity
Thought question
What is the structureof matter?
Atomic terminology
Phases & Pressure
Internal energy
Read: Chap 5 09/25/12 – slide 5
What can make an object gain
or lose orbital energy?
Friction or atmospheric
drag
A gravitational encounter.
Tides
Announcements
Orbits: summary
⊲ Tides
Experience
Interaction
Reflect/Scatter
Light/Matter
Thought question
Why Study Light?
Light as particles
Light as particles
Speed of light
Light as waves
Wave propagation
EM Radiation
Infrared
Energy & Intensity
Summary
Intensity
Thought question
What is the structureof matter?
Atomic terminology
Phases & Pressure
Internal energy
Read: Chap 5 09/25/12 – slide 6
How does gravity cause tides?
Moon’s gravity pulls harder on near side of Earth than on
far side
Difference in Moons gravitational pull stretches Earth
Tides and Phases
Announcements
Orbits: summary
⊲ Tides
Experience
Interaction
Reflect/Scatter
Light/Matter
Thought question
Why Study Light?
Light as particles
Light as particles
Speed of light
Light as waves
Wave propagation
EM Radiation
Infrared
Energy & Intensity
Summary
Intensity
Thought question
What is the structureof matter?
Atomic terminology
Phases & Pressure
Internal energy
Read: Chap 5 09/25/12 – slide 7
Size of tides
depends on
phase of
Moon
Tidal Friction
Announcements
Orbits: summary
⊲ Tides
Experience
Interaction
Reflect/Scatter
Light/Matter
Thought question
Why Study Light?
Light as particles
Light as particles
Speed of light
Light as waves
Wave propagation
EM Radiation
Infrared
Energy & Intensity
Summary
Intensity
Thought question
What is the structureof matter?
Atomic terminology
Phases & Pressure
Internal energy
Read: Chap 5 09/25/12 – slide 8
Tidal friction gradually slows Earth rotation (and makes
Moon get farther from Earth).
Moon once orbited faster (or slower); tidal friction
caused it to lock in synchronous rotation.
How do we experience light?
Announcements
Orbits: summary
Tides
⊲ Experience
Interaction
Reflect/Scatter
Light/Matter
Thought question
Why Study Light?
Light as particles
Light as particles
Speed of light
Light as waves
Wave propagation
EM Radiation
Infrared
Energy & Intensity
Summary
Intensity
Thought question
What is the structureof matter?
Atomic terminology
Phases & Pressure
Internal energy
Read: Chap 5 09/25/12 – slide 10
The warmth of sunlight: light is a form of energy
Energy flow is measured in watts: 1 watt = 1 joule/s
How do we experience light?
Announcements
Orbits: summary
Tides
⊲ Experience
Interaction
Reflect/Scatter
Light/Matter
Thought question
Why Study Light?
Light as particles
Light as particles
Speed of light
Light as waves
Wave propagation
EM Radiation
Infrared
Energy & Intensity
Summary
Intensity
Thought question
What is the structureof matter?
Atomic terminology
Phases & Pressure
Internal energy
Read: Chap 5 09/25/12 – slide 10
The warmth of sunlight: light is a form of energy
Energy flow is measured in watts: 1 watt = 1 joule/s
One joule in everyday life is approximately:
⊲ Energy required to lift up a small apple one meter
(100 g ≈ 1/9.8 kg)
⊲ Energy released when the apple falls one meter
⊲ The energy released as heat by a person every
1/60th of a second
⊲ Kinetic energy of a 50 kg human moving slowly
(0.2 m/s)
⊲ Kinetic energy of a tennis ball at 23 km/h (14 mph)
How do we experience light?
Announcements
Orbits: summary
Tides
⊲ Experience
Interaction
Reflect/Scatter
Light/Matter
Thought question
Why Study Light?
Light as particles
Light as particles
Speed of light
Light as waves
Wave propagation
EM Radiation
Infrared
Energy & Intensity
Summary
Intensity
Thought question
What is the structureof matter?
Atomic terminology
Phases & Pressure
Internal energy
Read: Chap 5 09/25/12 – slide 10
The warmth of sunlight: light is a form of energy
Energy flow is measured in watts: 1 watt = 1 joule/s
White light is made up of different colors
How do we experience light?
Announcements
Orbits: summary
Tides
⊲ Experience
Interaction
Reflect/Scatter
Light/Matter
Thought question
Why Study Light?
Light as particles
Light as particles
Speed of light
Light as waves
Wave propagation
EM Radiation
Infrared
Energy & Intensity
Summary
Intensity
Thought question
What is the structureof matter?
Atomic terminology
Phases & Pressure
Internal energy
Read: Chap 5 09/25/12 – slide 10
The warmth of sunlight: light is a form of energy
Energy flow is measured in watts: 1 watt = 1 joule/s
White light is made up of different colors
How do light and matter interact?
Announcements
Orbits: summary
Tides
Experience
⊲ Interaction
Reflect/Scatter
Light/Matter
Thought question
Why Study Light?
Light as particles
Light as particles
Speed of light
Light as waves
Wave propagation
EM Radiation
Infrared
Energy & Intensity
Summary
Intensity
Thought question
What is the structureof matter?
Atomic terminology
Phases & Pressure
Internal energy
Read: Chap 5 09/25/12 – slide 11
Emission
Absorption
Transmission
⊲ Transparent objects transmit light
⊲ Opaque objects block (absorb) light
Reflection or Scattering
Reflection and scattering
Announcements
Orbits: summary
Tides
Experience
Interaction
⊲ Reflect/Scatter
Light/Matter
Thought question
Why Study Light?
Light as particles
Light as particles
Speed of light
Light as waves
Wave propagation
EM Radiation
Infrared
Energy & Intensity
Summary
Intensity
Thought question
What is the structureof matter?
Atomic terminology
Phases & Pressure
Internal energy
Read: Chap 5 09/25/12 – slide 12
Mirror reflects
light in a partic-
ular direction
Movie screen reflects light in many direc-
tions
Interaction of Light and Matter
Announcements
Orbits: summary
Tides
Experience
Interaction
Reflect/Scatter
⊲ Light/Matter
Thought question
Why Study Light?
Light as particles
Light as particles
Speed of light
Light as waves
Wave propagation
EM Radiation
Infrared
Energy & Intensity
Summary
Intensity
Thought question
What is the structureof matter?
Atomic terminology
Phases & Pressure
Internal energy
Read: Chap 5 09/25/12 – slide 13
Interactions between light and matter determine the
appearance of everything around us
Thought question
Announcements
Orbits: summary
Tides
Experience
Interaction
Reflect/Scatter
Light/Matter
⊲ Thought question
Why Study Light?
Light as particles
Light as particles
Speed of light
Light as waves
Wave propagation
EM Radiation
Infrared
Energy & Intensity
Summary
Intensity
Thought question
What is the structureof matter?
Atomic terminology
Phases & Pressure
Internal energy
Read: Chap 5 09/25/12 – slide 14
Why is a rose red?
The rose absorbs red light.
The rose transmits red light.
The rose emits red light.
The rose reflects red light.
Thought question
Announcements
Orbits: summary
Tides
Experience
Interaction
Reflect/Scatter
Light/Matter
⊲ Thought question
Why Study Light?
Light as particles
Light as particles
Speed of light
Light as waves
Wave propagation
EM Radiation
Infrared
Energy & Intensity
Summary
Intensity
Thought question
What is the structureof matter?
Atomic terminology
Phases & Pressure
Internal energy
Read: Chap 5 09/25/12 – slide 14
Why is a rose red?
The rose absorbs red light.
The rose transmits red light.
The rose emits red light.
The rose reflects red light.
Why Study Light?
Announcements
Orbits: summary
Tides
Experience
Interaction
Reflect/Scatter
Light/Matter
Thought question
⊲ Why Study Light?
Light as particles
Light as particles
Speed of light
Light as waves
Wave propagation
EM Radiation
Infrared
Energy & Intensity
Summary
Intensity
Thought question
What is the structureof matter?
Atomic terminology
Phases & Pressure
Internal energy
Read: Chap 5 09/25/12 – slide 15
Astronomy is passive science —
Why Study Light?
Announcements
Orbits: summary
Tides
Experience
Interaction
Reflect/Scatter
Light/Matter
Thought question
⊲ Why Study Light?
Light as particles
Light as particles
Speed of light
Light as waves
Wave propagation
EM Radiation
Infrared
Energy & Intensity
Summary
Intensity
Thought question
What is the structureof matter?
Atomic terminology
Phases & Pressure
Internal energy
Read: Chap 5 09/25/12 – slide 15
Astronomy is passive science — observations!
Can only VISIT most nearby celestial objects
Want knowledge of physical properties!
Why Study Light?
Announcements
Orbits: summary
Tides
Experience
Interaction
Reflect/Scatter
Light/Matter
Thought question
⊲ Why Study Light?
Light as particles
Light as particles
Speed of light
Light as waves
Wave propagation
EM Radiation
Infrared
Energy & Intensity
Summary
Intensity
Thought question
What is the structureof matter?
Atomic terminology
Phases & Pressure
Internal energy
Read: Chap 5 09/25/12 – slide 15
Astronomy is passive science — observations!
Can only VISIT most nearby celestial objects
Want knowledge of physical properties!
Using light we can determine the following properties:
⊲ Temperature
⊲ Composition
⊲ Velocity
Light as particles
Announcements
Orbits: summary
Tides
Experience
Interaction
Reflect/Scatter
Light/Matter
Thought question
Why Study Light?
⊲ Light as particles
Light as particles
Speed of light
Light as waves
Wave propagation
EM Radiation
Infrared
Energy & Intensity
Summary
Intensity
Thought question
What is the structureof matter?
Atomic terminology
Phases & Pressure
Internal energy
Read: Chap 5 09/25/12 – slide 16
Light travels through empty space at a speed of
c = 300, 000 km/s
Olaus Romer (1676) dis-
covered that eclipse tim-
ing depended on distance
of Earth to Jupiter
Implies a speed of light
propagating in a vacuum
Light as particles
Announcements
Orbits: summary
Tides
Experience
Interaction
Reflect/Scatter
Light/Matter
Thought question
Why Study Light?
⊲ Light as particles
Light as particles
Speed of light
Light as waves
Wave propagation
EM Radiation
Infrared
Energy & Intensity
Summary
Intensity
Thought question
What is the structureof matter?
Atomic terminology
Phases & Pressure
Internal energy
Read: Chap 5 09/25/12 – slide 16
Light travels through empty space at a speed of
c = 300, 000 km/s
Olaus Romer (1676) dis-
covered that eclipse tim-
ing depended on distance
of Earth to Jupiter
Implies a speed of light
propagating in a vacuum
Galileo tried to mea-
sure speed of light with
lanterns on mountain-
tops!
Light as particles
Announcements
Orbits: summary
Tides
Experience
Interaction
Reflect/Scatter
Light/Matter
Thought question
Why Study Light?
Light as particles
⊲ Light as particles
Speed of light
Light as waves
Wave propagation
EM Radiation
Infrared
Energy & Intensity
Summary
Intensity
Thought question
What is the structureof matter?
Atomic terminology
Phases & Pressure
Internal energy
Read: Chap 5 09/25/12 – slide 17
Romer’s drawing
Speed of light in the lab
Announcements
Orbits: summary
Tides
Experience
Interaction
Reflect/Scatter
Light/Matter
Thought question
Why Study Light?
Light as particles
Light as particles
⊲ Speed of light
Light as waves
Wave propagation
EM Radiation
Infrared
Energy & Intensity
Summary
Intensity
Thought question
What is the structureof matter?
Atomic terminology
Phases & Pressure
Internal energy
Read: Chap 5 09/25/12 – slide 18
Fizeau and Foucalt (1850) measured speed of light by
bouncing a beam off of a rotating mirror
Mirror moves as light travels
The light returns to its source at a different position
Speed of light in the lab
Announcements
Orbits: summary
Tides
Experience
Interaction
Reflect/Scatter
Light/Matter
Thought question
Why Study Light?
Light as particles
Light as particles
⊲ Speed of light
Light as waves
Wave propagation
EM Radiation
Infrared
Energy & Intensity
Summary
Intensity
Thought question
What is the structureof matter?
Atomic terminology
Phases & Pressure
Internal energy
Read: Chap 5 09/25/12 – slide 18
Fizeau and Foucalt (1850) measured speed of light by
bouncing a beam off of a rotating mirror
Mirror moves as light travels
The light returns to its source at a different position
To summarize:
Light has a well-defined speed,
as if it were made of bullets!
Light as waves
Announcements
Orbits: summary
Tides
Experience
Interaction
Reflect/Scatter
Light/Matter
Thought question
Why Study Light?
Light as particles
Light as particles
Speed of light
⊲ Light as waves
Wave propagation
EM Radiation
Infrared
Energy & Intensity
Summary
Intensity
Thought question
What is the structureof matter?
Atomic terminology
Phases & Pressure
Internal energy
Read: Chap 5 09/25/12 – slide 19
Light is composed of all colors (rainbow).
How and Why?
Light as waves
Announcements
Orbits: summary
Tides
Experience
Interaction
Reflect/Scatter
Light/Matter
Thought question
Why Study Light?
Light as particles
Light as particles
Speed of light
⊲ Light as waves
Wave propagation
EM Radiation
Infrared
Energy & Intensity
Summary
Intensity
Thought question
What is the structureof matter?
Atomic terminology
Phases & Pressure
Internal energy
Read: Chap 5 09/25/12 – slide 20
Isaac Newton suggested that light was made of tiny
particles called PHOTONS
Attempted to explain spectrum using properties of the
particles
Light as waves
Announcements
Orbits: summary
Tides
Experience
Interaction
Reflect/Scatter
Light/Matter
Thought question
Why Study Light?
Light as particles
Light as particles
Speed of light
⊲ Light as waves
Wave propagation
EM Radiation
Infrared
Energy & Intensity
Summary
Intensity
Thought question
What is the structureof matter?
Atomic terminology
Phases & Pressure
Internal energy
Read: Chap 5 09/25/12 – slide 21
“Nothing is more
requisite for produc-
ing all the variety of
Colours, and degrees
of Refrangibility than
that the Rays of Light
be Bodies of different
Sizes, the least of
which may take vio-
let the weakest and darkest of the Colours, and be more easily
diverted by refracting Surfaces from the right Course; and the
rest as they are bigger and bigger, may make the stronger and
more lucid colours, blue, green, yellow, and red, and be more
and more difficultly diverted.”
Sir Issac Newton, Opticks
Light as waves
Announcements
Orbits: summary
Tides
Experience
Interaction
Reflect/Scatter
Light/Matter
Thought question
Why Study Light?
Light as particles
Light as particles
Speed of light
⊲ Light as waves
Wave propagation
EM Radiation
Infrared
Energy & Intensity
Summary
Intensity
Thought question
What is the structureof matter?
Atomic terminology
Phases & Pressure
Internal energy
Read: Chap 5 09/25/12 – slide 22
Young (1801): light has wave-like properties.
Light passing through two narrow slits which resulted in
a pattern of bright and dark bands
Light as waves
Announcements
Orbits: summary
Tides
Experience
Interaction
Reflect/Scatter
Light/Matter
Thought question
Why Study Light?
Light as particles
Light as particles
Speed of light
⊲ Light as waves
Wave propagation
EM Radiation
Infrared
Energy & Intensity
Summary
Intensity
Thought question
What is the structureof matter?
Atomic terminology
Phases & Pressure
Internal energy
Read: Chap 5 09/25/12 – slide 22
Young (1801): light has wave-like properties.
Light passing through two narrow slits which resulted in
a pattern of bright and dark bands
Light as waves
Announcements
Orbits: summary
Tides
Experience
Interaction
Reflect/Scatter
Light/Matter
Thought question
Why Study Light?
Light as particles
Light as particles
Speed of light
⊲ Light as waves
Wave propagation
EM Radiation
Infrared
Energy & Intensity
Summary
Intensity
Thought question
What is the structureof matter?
Atomic terminology
Phases & Pressure
Internal energy
Read: Chap 5 09/25/12 – slide 22
Young (1801): light has wave-like properties.
Light passing through two narrow slits which resulted in
a pattern of bright and dark bands
Propagation of waves
Announcements
Orbits: summary
Tides
Experience
Interaction
Reflect/Scatter
Light/Matter
Thought question
Why Study Light?
Light as particles
Light as particles
Speed of light
Light as waves
⊲ Wave propagation
EM Radiation
Infrared
Energy & Intensity
Summary
Intensity
Thought question
What is the structureof matter?
Atomic terminology
Phases & Pressure
Internal energy
Read: Chap 5 09/25/12 – slide 23
wavelength: distance between crests
frequency: rate at which crests move past a fixed point
wavelength × frequency = speed
FM radio waves transmit information by changing the
frequency of the waves. Your radio can then create
sound by recognizing these changes in frequency.
Propagation of waves
Announcements
Orbits: summary
Tides
Experience
Interaction
Reflect/Scatter
Light/Matter
Thought question
Why Study Light?
Light as particles
Light as particles
Speed of light
Light as waves
⊲ Wave propagation
EM Radiation
Infrared
Energy & Intensity
Summary
Intensity
Thought question
What is the structureof matter?
Atomic terminology
Phases & Pressure
Internal energy
Read: Chap 5 09/25/12 – slide 23
wavelength: distance between crests
frequency: rate at which crests move past a fixed point
wavelength × frequency = speed
FM radio waves transmit information by changing the
frequency of the waves. Your radio can then create
sound by recognizing these changes in frequency.
Propagation of waves
Announcements
Orbits: summary
Tides
Experience
Interaction
Reflect/Scatter
Light/Matter
Thought question
Why Study Light?
Light as particles
Light as particles
Speed of light
Light as waves
⊲ Wave propagation
EM Radiation
Infrared
Energy & Intensity
Summary
Intensity
Thought question
What is the structureof matter?
Atomic terminology
Phases & Pressure
Internal energy
Read: Chap 5 09/25/12 – slide 24
Material does not move in the direction of wave
propagation!!
Example:
⊲ Bobber in water
⊲ Swimming in ocean
Waves move past the object . . .
Propagation of waves
Announcements
Orbits: summary
Tides
Experience
Interaction
Reflect/Scatter
Light/Matter
Thought question
Why Study Light?
Light as particles
Light as particles
Speed of light
Light as waves
⊲ Wave propagation
EM Radiation
Infrared
Energy & Intensity
Summary
Intensity
Thought question
What is the structureof matter?
Atomic terminology
Phases & Pressure
Internal energy
Read: Chap 5 09/25/12 – slide 24
Material does not move in the direction of wave
propagation!!
Example:
⊲ Bobber in water
⊲ Swimming in ocean
Waves move past the object . . .
What is the medium for light propagation?
Propagation of waves
Announcements
Orbits: summary
Tides
Experience
Interaction
Reflect/Scatter
Light/Matter
Thought question
Why Study Light?
Light as particles
Light as particles
Speed of light
Light as waves
⊲ Wave propagation
EM Radiation
Infrared
Energy & Intensity
Summary
Intensity
Thought question
What is the structureof matter?
Atomic terminology
Phases & Pressure
Internal energy
Read: Chap 5 09/25/12 – slide 24
Material does not move in the direction of wave
propagation!!
Example:
⊲ Bobber in water
⊲ Swimming in ocean
Waves move past the object . . .
What is the medium for light propagation?
Luminiferous Aether: a massless vapor that filled the
Universe (19th century) to propagate heat and light
Electromagnetic radiation
Announcements
Orbits: summary
Tides
Experience
Interaction
Reflect/Scatter
Light/Matter
Thought question
Why Study Light?
Light as particles
Light as particles
Speed of light
Light as waves
Wave propagation
⊲ EM Radiation
Infrared
Energy & Intensity
Summary
Intensity
Thought question
What is the structureof matter?
Atomic terminology
Phases & Pressure
Internal energy
Read: Chap 5 09/25/12 – slide 25
Electromagnetic waves are waves of energy that travel
through space at the speed of light
Consist of combined electric and magnetic waves that
result when a charged particle accelerates
The acceleration creates a wave with both electric and
magnetic components
Electromagnetic radiation
Announcements
Orbits: summary
Tides
Experience
Interaction
Reflect/Scatter
Light/Matter
Thought question
Why Study Light?
Light as particles
Light as particles
Speed of light
Light as waves
Wave propagation
⊲ EM Radiation
Infrared
Energy & Intensity
Summary
Intensity
Thought question
What is the structureof matter?
Atomic terminology
Phases & Pressure
Internal energy
Read: Chap 5 09/25/12 – slide 26
Astronomically important
frequencies range from:
◦ 102 Hz (low) to 1024
Hz (high)
Astronomically important
wavelengths range from:
◦ 108 cm (long) to
10−14 cm (short)
William Herschel and Infrared
Announcements
Orbits: summary
Tides
Experience
Interaction
Reflect/Scatter
Light/Matter
Thought question
Why Study Light?
Light as particles
Light as particles
Speed of light
Light as waves
Wave propagation
EM Radiation
⊲ Infrared
Energy & Intensity
Summary
Intensity
Thought question
What is the structureof matter?
Atomic terminology
Phases & Pressure
Internal energy
Read: Chap 5 09/25/12 – slide 27
Circa 1800: used mercury ther-
mometers to measure the en-
ergy in different colors of light
Highest temperature was just
beyond the red part of the spec-
trum
Discovered energy beyond the
visible spectrum: infrared!
Energy and Intensity of Light
Announcements
Orbits: summary
Tides
Experience
Interaction
Reflect/Scatter
Light/Matter
Thought question
Why Study Light?
Light as particles
Light as particles
Speed of light
Light as waves
Wave propagation
EM Radiation
Infrared
⊲Energy &Intensity
Summary
Intensity
Thought question
What is the structureof matter?
Atomic terminology
Phases & Pressure
Internal energy
Read: Chap 5 09/25/12 – slide 28
Energy carried by a photon is proportional to its
frequency
E = hν = hc/λ
Planck’s constant:
h = 6.63× 10−34 Joule-sec
Therefore, the total energy carried by a beam of light (its
intensity) depends both on the number of photons per
second and their frequency
Properties of Light: Summary
Announcements
Orbits: summary
Tides
Experience
Interaction
Reflect/Scatter
Light/Matter
Thought question
Why Study Light?
Light as particles
Light as particles
Speed of light
Light as waves
Wave propagation
EM Radiation
Infrared
Energy & Intensity
⊲ Summary
Intensity
Thought question
What is the structureof matter?
Atomic terminology
Phases & Pressure
Internal energy
Read: Chap 5 09/25/12 – slide 29
Particle properties
⊲ Travels in straight lines (bullets)
⊲ “Rays” are parallel far from source
⊲ E = hν
Wave properties
⊲ “Rainbow” spectrum
⊲ Interference
Light is electromagnetic radiation
Wave-Particle Duality: light has both wave-like and
particle-like properties!
Energy and Intensity of Light
Announcements
Orbits: summary
Tides
Experience
Interaction
Reflect/Scatter
Light/Matter
Thought question
Why Study Light?
Light as particles
Light as particles
Speed of light
Light as waves
Wave propagation
EM Radiation
Infrared
Energy & Intensity
Summary
⊲ Intensity
Thought question
What is the structureof matter?
Atomic terminology
Phases & Pressure
Internal energy
Read: Chap 5 09/25/12 – slide 30
Energy carried by a photon is proportional to its
frequency
E = hν = hc/λ
Planck’s constant:
h = 6.63× 10−34 Joule-sec
Therefore, the total energy carried by a beam of light (its
intensity) depends both on the number of photons per
second and their frequency
Thought question
Announcements
Orbits: summary
Tides
Experience
Interaction
Reflect/Scatter
Light/Matter
Thought question
Why Study Light?
Light as particles
Light as particles
Speed of light
Light as waves
Wave propagation
EM Radiation
Infrared
Energy & Intensity
Summary
Intensity
⊲ Thought question
What is the structureof matter?
Atomic terminology
Phases & Pressure
Internal energy
Read: Chap 5 09/25/12 – slide 31
Question: Is there an interference pattern if I fired one photon
at at time at the double slits?
Thought question
Announcements
Orbits: summary
Tides
Experience
Interaction
Reflect/Scatter
Light/Matter
Thought question
Why Study Light?
Light as particles
Light as particles
Speed of light
Light as waves
Wave propagation
EM Radiation
Infrared
Energy & Intensity
Summary
Intensity
⊲ Thought question
What is the structureof matter?
Atomic terminology
Phases & Pressure
Internal energy
Read: Chap 5 09/25/12 – slide 31
Question: Is there an interference pattern if I fired one photon
at at time at the double slits? Yes
Thought question
Announcements
Orbits: summary
Tides
Experience
Interaction
Reflect/Scatter
Light/Matter
Thought question
Why Study Light?
Light as particles
Light as particles
Speed of light
Light as waves
Wave propagation
EM Radiation
Infrared
Energy & Intensity
Summary
Intensity
⊲ Thought question
What is the structureof matter?
Atomic terminology
Phases & Pressure
Internal energy
Read: Chap 5 09/25/12 – slide 31
Question: Is there an interference pattern if I fired one photon
at at time at the double slits?
Particle-wave duality
Thought question
Announcements
Orbits: summary
Tides
Experience
Interaction
Reflect/Scatter
Light/Matter
Thought question
Why Study Light?
Light as particles
Light as particles
Speed of light
Light as waves
Wave propagation
EM Radiation
Infrared
Energy & Intensity
Summary
Intensity
⊲ Thought question
What is the structureof matter?
Atomic terminology
Phases & Pressure
Internal energy
Read: Chap 5 09/25/12 – slide 32
The higher the photon energy . . .
the longer its wavelength.
the shorter its wavelength.
energy is independent of wavelength.
Thought question
Announcements
Orbits: summary
Tides
Experience
Interaction
Reflect/Scatter
Light/Matter
Thought question
Why Study Light?
Light as particles
Light as particles
Speed of light
Light as waves
Wave propagation
EM Radiation
Infrared
Energy & Intensity
Summary
Intensity
⊲ Thought question
What is the structureof matter?
Atomic terminology
Phases & Pressure
Internal energy
Read: Chap 5 09/25/12 – slide 32
The higher the photon energy . . .
the longer its wavelength.
the shorter its wavelength.
energy is independent of wavelength.
What is the structure of matter?
Announcements
Orbits: summary
Tides
Experience
Interaction
Reflect/Scatter
Light/Matter
Thought question
Why Study Light?
Light as particles
Light as particles
Speed of light
Light as waves
Wave propagation
EM Radiation
Infrared
Energy & Intensity
Summary
Intensity
Thought question
⊲
What is thestructure ofmatter?
Atomic terminology
Phases & Pressure
Internal energy
Read: Chap 5 09/25/12 – slide 33
[Atom] [Electron cloud] [Nucleus]
Atomic terminology
Announcements
Orbits: summary
Tides
Experience
Interaction
Reflect/Scatter
Light/Matter
Thought question
Why Study Light?
Light as particles
Light as particles
Speed of light
Light as waves
Wave propagation
EM Radiation
Infrared
Energy & Intensity
Summary
Intensity
Thought question
What is the structureof matter?
⊲Atomicterminology
Phases & Pressure
Internal energy
Read: Chap 5 09/25/12 – slide 34
Atomic Number = # of protons in nucleus
Atomic Mass Number = # of protons + neutrons
Molecules: consist of two or more atoms (H2O,CO2)
Atomic terminology
Announcements
Orbits: summary
Tides
Experience
Interaction
Reflect/Scatter
Light/Matter
Thought question
Why Study Light?
Light as particles
Light as particles
Speed of light
Light as waves
Wave propagation
EM Radiation
Infrared
Energy & Intensity
Summary
Intensity
Thought question
What is the structureof matter?
⊲Atomicterminology
Phases & Pressure
Internal energy
Read: Chap 5 09/25/12 – slide 35
Isotope: same # of protons but different # of neutrons.
(4He, 3He)
Phases & Pressure
Announcements
Orbits: summary
Tides
Experience
Interaction
Reflect/Scatter
Light/Matter
Thought question
Why Study Light?
Light as particles
Light as particles
Speed of light
Light as waves
Wave propagation
EM Radiation
Infrared
Energy & Intensity
Summary
Intensity
Thought question
What is the structureof matter?
Atomic terminology
⊲ Phases & Pressure
Internal energy
Read: Chap 5 09/25/12 – slide 36
Example: familiar phases (of water)
Solid (ice)
Liquid (water)
Gas (water vapor)
Phases of same material behave differently because of
differences in chemical bonds
Phases & Pressure
Announcements
Orbits: summary
Tides
Experience
Interaction
Reflect/Scatter
Light/Matter
Thought question
Why Study Light?
Light as particles
Light as particles
Speed of light
Light as waves
Wave propagation
EM Radiation
Infrared
Energy & Intensity
Summary
Intensity
Thought question
What is the structureof matter?
Atomic terminology
⊲ Phases & Pressure
Internal energy
Read: Chap 5 09/25/12 – slide 36
Example: familiar phases (of water)
Solid (ice)
Liquid (water)
Gas (water vapor)
Phases of same material behave differently because of
differences in chemical bonds Less familiar phase:
Ionized (plasma)
Phases & Pressure
Announcements
Orbits: summary
Tides
Experience
Interaction
Reflect/Scatter
Light/Matter
Thought question
Why Study Light?
Light as particles
Light as particles
Speed of light
Light as waves
Wave propagation
EM Radiation
Infrared
Energy & Intensity
Summary
Intensity
Thought question
What is the structureof matter?
Atomic terminology
⊲ Phases & Pressure
Internal energy
Read: Chap 5 09/25/12 – slide 37
Ionization: Stripping of electrons,
changing atoms into plasma
Dissociation: Breaking of molecules
into atoms
Evaporation: Breaking of flexible
chemical bonds, changing liquid into
solid
Melting: Breaking of rigid chemical
bonds, changing solid into liquid
Phases & Pressure
Announcements
Orbits: summary
Tides
Experience
Interaction
Reflect/Scatter
Light/Matter
Thought question
Why Study Light?
Light as particles
Light as particles
Speed of light
Light as waves
Wave propagation
EM Radiation
Infrared
Energy & Intensity
Summary
Intensity
Thought question
What is the structureof matter?
Atomic terminology
⊲ Phases & Pressure
Internal energy
Read: Chap 5 09/25/12 – slide 38
Phase of a substance depends on both temperature and
pressure
Often more than one phase is present
Internal energy
Announcements
Orbits: summary
Tides
Experience
Interaction
Reflect/Scatter
Light/Matter
Thought question
Why Study Light?
Light as particles
Light as particles
Speed of light
Light as waves
Wave propagation
EM Radiation
Infrared
Energy & Intensity
Summary
Intensity
Thought question
What is the structureof matter?
Atomic terminology
Phases & Pressure
⊲ Internal energy
Read: Chap 5 09/25/12 – slide 39
How much energy is stored in atoms?
Electrons in atoms are restricted to particular energy
levels
Internal energy
Read: Chap 5 09/25/12 – slide 40
Energy Level Transitions
The only allowed
changes in en-
ergy are those
corresponding
to a transition
between energy
levels
Internal energy
Read: Chap 5 09/25/12 – slide 40
Energy Level Transitions
Disallowed!
The only allowed
changes in en-
ergy are those
corresponding
to a transition
between energy
levels
Internal energy
Read: Chap 5 09/25/12 – slide 40
Energy Level Transitions
Disallowed! Allowed!
The only allowed
changes in en-
ergy are those
corresponding
to a transition
between energy
levels
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