1.1.3 Explain how the sun produces energy which is transferred to the Earth by radiation. Sun’s Energy

Combustion and Nuclear Reactions 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. Combustion and Nuclear Reactions

Table: Fission Fusion Definition Natural process Byproducts Conditions Energy requirements Energy released Weapons

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

Natural Processes Fission reaction does not normally occur in nature. Except for radio active decay Fusion occurs in stars, such as the sun.

Byproducts of the reaction Fission produces many highly radioactive particles. Fusion produces few radioactive particles are produced by fusion reaction, but if a fission "trigger" is used, radioactive particles will result from that.

Conditions 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.

Energy Requirements Takes little energy to split two atoms in a fission reaction. Fusion takes extremely high energy to bring two or more protons close enough that nuclear forces overcome their electrostatic repulsion.

Energy Released 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.

Nuclear Weapons 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.

Energy Produced by the Sun 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.). Energy Produced by the Sun

What is an Electromagnetic Wave? 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

Producing Electromagnetic Waves Electromagnetic waves are produced by charged particles Electromagnetic waves can travel through the vacuum of space.

Tools of Astronomy Radiation It includes visible light, infrared and ultraviolet radiation, radio waves, microwaves, X rays, and gamma rays.

Speed 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

Particle Model of Light 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