Transcript Combustion and Nuclear Reactions

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Draw a diagram of the relative positions of
the sun, moon, and Earth during a
 Full moon
 New moon
1.1.3 Explain how the sun produces energy which is transferred to the
Earth by radiation.
1.1.3a Compare combustion and nuclear reactions (fusion and fission) on a
conceptual level. Identify fusion as the process that produces radiant
energy of stars.
Fission
Definition
Fusion
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Fission is the splitting of a
large atom into two or more
smaller ones.
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Fusion is the fusing of two or
more lighter atoms into a
larger one.
 Fusion demo
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Fission reaction does not
normally occur in nature.
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Fusion occurs in stars, such as
the sun.
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Fission produces many highly radioactive
particles.
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Few radioactive particles are produced by
fusion reaction, but if a fission "trigger" is
used, radioactive particles will result from
that.
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Critical mass of the substance and high-speed
neutrons are required for fission. (Think
“enriched” uranium)
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High density, high temperature environment
is required for fusion.
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Takes little energy to split two atoms in a
fission reaction.
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Extremely high energy is required to bring
two or more protons close enough that
nuclear forces overcome their electrostatic
repulsion.
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The energy released by fission is a million
times greater than that released in chemical
reactions; but lower than the energy released
by nuclear fusion.
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The energy released by fusion is three to four
times greater than the energy released by
fission.
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One class of nuclear weapon
is a fission bomb, also known
as an atomic bomb or atom
bomb.
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One class of nuclear weapon
is the hydrogen bomb, which
uses a fission reaction to
"trigger" a fusion reaction.
1.1.3b Identify the forms of energy (electromagnetic waves) produced by
the sun and how some are filtered by the atmosphere (X-rays, cosmic rays,
etc.).
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What is the difference between fusion and
fission?
Which one occurs on the sun?
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Electromagnetic waves can transfer energy
without a medium
An electromagnetic wave consists of
vibrating electric and magnetic fields that
move through space at the speed of light
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Electromagnetic waves are produced by
charged particles
Every charged particle has an electric field
surrounding it
The electric field produces electric forces that
can push or pull on other particles
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When a charged particle moves it produces a
Magnetic field
 A magnetic field can exert magnetic forces that
can act on certain materials
 Example:
▪ If you place a paper clip near a magnet, the paper clip
will move toward the magnet because of the magnetic
field surrounding the magnet.
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When a charged particle changes its motion,
its magnetic field changes
The changing magnetic field causes the
electric field to change
When one field vibrates, so does the other
**The two fields constantly causes each
other to change and this produces an
Electromagnetic wave**
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Electromagnetic Radiation is the energy
that is transferred through space by
electromagnetic waves
Electromagnetic waves transfer energy
through a vacuum, or empty space
 Example: You can see the stars and sun because
their light reaches the Earth through the vacuum
of space
Tools of Astronomy
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It includes visible light, infrared and
ultraviolet radiation, radio waves,
microwaves, X rays, and gamma rays.
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All electromagnetic waves travel at the same
speed in a vacuum = 300,000 km/s
This speed is called the speed of light
 At this speed, light from the sun takes about 8
minutes to travel to the Earth (150 km)
 Light waves travel more slowly in air
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Many properties of electromagnetic waves
can be explained by a wave model
Some properties are best explained by a
particle model
Both a wave model and a particle model are
needed to explain all of the properties light
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Light acts as a wave when it passes through a
polarizing filter
Ordinary light has waves that vibrate in all
directions-up and down, left and right, and at
all other angles
A polarizing filter acts as though it has tiny
slits that are aligned in one direction
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Only some light waves pass through a
polarizing filter.
Light that passes through and vibrates in only
one direction is called polarized light
No light passes through two polarizing filters
that are placed at right angles to each other
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To better understand the wave model of light…
 Think of waves of light as being transverse waves on a
rope
 If you shake a rope through a fence with vertical slats,
only waves that vibrate up and down will pass through
 If you shake the rope side to side, the waves will be
blocked
 A polarizing light filter acts like the slats in a fence.
▪ It only allows waves that vibrate in one direction to pass
through
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Sometimes light behaves like a stream of
particles
When a beam of light shines on some
substances it causes tiny particles called
electrons to move
 The movement of electrons causes an electric
current to flow
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Sometimes light can even cause an electron
to move so much that it is knocked out of the
substance
 This process is called the photoelectric effect
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The photoelectric effect can be explained
only by thinking of light as a stream of tiny
packets, or particles of energy
 Each packet of light energy is called a photon
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Albert Einstein first explained the science
behind the photoelectric effect in 1905