 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.

FissionFusion Definition

 Fission is the splitting of a large atom into two or more smaller ones.  Fusion is the fusing of two or more lighter atoms into a larger one.  Fusion demo Fusion demo

 Fission reaction does not normally occur in nature.  Fusion occurs in stars, such as the sun.

 Fission produces many highly radioactive particles.  Few radioactive particles are produced by fusion reaction, but if a fission "trigger" is used, radioactive particles will result from that.

 Critical mass of the substance and high-speed neutrons are required for fission. (Think “enriched” uranium)  High density, high temperature environment is required for fusion.

 Takes little energy to split two atoms in a fission reaction.  Extremely high energy is required to bring two or more protons close enough that nuclear forces overcome their electrostatic repulsion.

 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.  The energy released by fusion is three to four times greater than the energy released by fission.

 One class of nuclear weapon is a fission bomb, also known as an atomic bomb or atom bomb.  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.).

 What is the difference between fusion and fission?  Which one occurs on the sun?

 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

 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

 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.

 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**

 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  It includes visible light, infrared and ultraviolet radiation, radio waves, microwaves, X rays, and gamma rays.

 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

 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

 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

 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

 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

 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

 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

 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  Albert Einstein first explained the science behind the photoelectric effect in 1905