Astronomy Picture of the Day

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Astronomy Picture of the Day
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Notes

• CPS Troubleshooting Times
• Josh Stephenson Regener Hall Rm. 111
• Monday 1250 100 / 150 230 / 345 400
• Wednesday 1250 100 / 150 230 / 345
  400
• Friday 150 500
• Brahe Likely Died of Mercury Poisoning
• The first test will be on Monday, Feb. 21
• Today Finish Ch. 1 and start Ch. 2

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Orbit of Earth around Sun(Demo - Ball on String)
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Gravity and Orbits

• Throwing an object fast enough will put the
  object into orbit! (Neglecting air resistance)
• Moon is continually falling towards the Earth
  in its orbit (Gravity vs. inertia)

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Correction to Keplers Third Law

• Earth and sun actually rotate about their common
  center of mass
• Corresponds to a point inside sun
• Used to detect extrasolar planets

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CPS Question

• The force of gravity between two objects varies
  with the
• A) product of the two masses.
• B) inverse of the distance separating the two
  bodies.
• C) inverse square of the distance separating the
  two bodies.
• D) Both A and B are correct.
• E) Both A and C are correct.

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CPS Question

• The acceleration experienced by a falling object
  due to Earth's gravity _____ the mass of the
  object.
• A) increases with
• B) decreases with
• C) is independent of

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CPS Question

• A Mars-sized and a Jupiter-sized planet both
  orbit a star at the same distance. The
  Mars-sized planet has ______ orbital period when
  compared to that of the Jupiter-sized planet.
• A) a shorter
• B) a longer
• C) the same

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Chapter 2 EM Waves

• What is a wave?
• What are the main properties of waves?
• What two things do all waves transport?

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Waves are a type of disturbance that can
propagate or travel. Waves carry information and
energy.
Properties of a wave
wavelength (?)
crest
amplitude (A)
trough
velocity (v)
? is a distance, so its units are m, cm, or mm,
etc. Period (T) time between crest (or trough)
passages Frequency (f) rate of passage of
crests (or troughs), f???
V ????f?
1 T
(units Hertz or cycles/sec)
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Refraction
Waves bend when they pass through material
of different densities.
air
water
swimming pool
prism
glass
air
air
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All radiation (including visible light) travels
as Electromagnetic waves.
That is, waves of electric and magnetic fields
travelling together.
What are some examples of objects with magnetic
fields
What are some examples of objects with electric
fields
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All radiation (including visible light) travels
as Electromagnetic waves.
That is, waves of electric and magnetic fields
travelling together.
What are some examples of objects with magnetic
fields
a bar magnet the Earth the Sun
What are some examples of objects with electric
fields

protons electrons
"charged" particles that make up atoms.
Anything with too many or to few electrons!
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• Electric Force - opposites attract, likes repel
• Oscillating charges radiate
• All objects have temperatures greater than
  absolute zero - random thermal motion
• All objects radiate!
• Why dont we see the radiation coming from many
  ordinary objects?
• Dog whistle analogy

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Electromagnetic Radiation
(How we get information about the cosmos)
What are some examples of electromagnetic
radiation and what are the different ways in
which we might experience them or make use of
them?
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Electromagnetic Radiation
(How we get information about the cosmos)
What are some examples of electromagnetic
radiation and what are the different ways in
which we might experience them or make use of
them?
Light (see) Infrared (heat) Ultraviolet (su
nburn) Microwaves (cooking, communication) AM
radio (communication) FM radio (communication)
TV signals (communication) Cell phone
signals (communication) X-rays (medial
applications)