What is Light?

v speed of wave f frequency (number of cycles per second) A amplitude Light is like a slinky wavelength (Greek letter lambda) c = 3 x 10 8 m/s = f In vacuum:

Different frequencies = different colors 400 nm 7.5×10 14 Hz 500 nm 6.0×10 14 Hz 600 nm 5.0×10 14 Hz 700 nm 4.3×10 14 Hz infrared ultraviolet

What waves do: Echo (reflect) Disperse (speed varies with wavelength) Refract (bend going from one medium to another) Interfere (when two or more waves add) - diffract - beat - resonate

Some Radioactive Surprises The paper you are writing on is radioactive. If you are not writing on paper, don't take too much solace…. Your chair is probably more radioactive than the paper Either you are radioactive, or you are dead. And have been so, for a long time. The alcohol consumed at the Dining Clubs is radioactive. The United States Bureau of Alcohol, Tobacco, and Firearms tests wine, gin, whisky, and vodka for radioactivity. If the product does not have sufficient radioactivity, it may not be legally sold in the United States.

induced fission fusion

1 neutron in 3 neutrons out First nuclear weapons and reactors used fission

Exponential Growth Grand Vizier presents his invention to the Sultan

Chain reaction A chain reaction occurs if more than one neutron goes on to cause another fission.

Why doesn’t uranium found naturally in the Earth undergo a chain reaction? World’s first nuclear reactor: Gabon

Oak Ridge, Tennessee. 60,000 workers worked for three years to separate 2 kilograms of uranium-235 from uranium-238.

Handball court under the bleachers at the University of Chicago, Uranium-235 is at the center of the stack of graphite blocks; the carbon acts as a moderator, slowing neutrons.

In a nuclear reactor, to draw out as much as energy possible: Slow neutrons are required because uranium is not very enriched. Neutrons can be slowed by bouncing them off of light nuclei, such as carbon nuclei. ADVANTAGE: By releasing energy slowly, don’t need so much enrichment

Cadmium is a control rod – a good absorber of neutrons.

The smaller the sphere, the greater the ratio of surface area to volume, and the greater the percentage of neutrons which escape the sphere before causing fission. Bomb – no time for slow neutrons Need highly enriched uranium and make it go off fast -- then the issue is getting a critical mass

"Little Boy", two feet in diameter, ten feet long, 9000 pounds, dropped on Hiroshima, Japan, was a uranium bomb, equivalent to 13,000 tons of explosive

Fat Boy: Plutonium highly radioactive; need less BUT tends to self-explode cannon does not work; use implosion (other tricks: neutron reflectors) – reduces critical mass 20,000 tons from 6 kg of Pu

Little Boy and Fat Man Fat Boy: Plutonium highly radioactive; tends to self-explode cannon does not work; use implosion (other tricks: neutron reflectors)

Hydrogen (Fusion) Bomb

1000 x Hiroshima = 13 MEGAtons