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Radiation is created by the motion of charged particles. All matter with a temperature greater than absolute zero will emit radiation. The movement of charges will produce electromagnetic radiation. There is a wide range of radiation which reflects the wide range of energies and accelerations of the charges in any piece of matter at a single temperature.

Some examples of thermal radiation are visible light and infrared light emitted by an incandescent light bulb, the infrared radiation emitted by animals and detectable with an infrared camera, and the cosmic microwave background radiation.

There are four main properties of thermal radiation

  • Thermal radiation emitted by a body at any temperature consists of a number of frequencies.
  • The dominant frequency range of the emitted radiation shifts to high frequencies as the temperature of the emitter increases.
  • The total amount of radiation of all frequencies increase steeply as the temperature rises. It gros as T4, where T is the absolute temperature of the body.
  • The rate of electromagnetic radiation emitted at a given frequency is proportional to the amount of absorption that would be experience by the source

Heat shielding calculation

How much more effective will a double layered heat shield (.1mm stainless steel outer shell (facing radiant heat source), .5 mm inner aluminum shell, and 4mm air gap) be at blocking thermal radiation then a single 2mm thick sheet of aluminum? (assume both heat shields are same size and in same environment.

Bremsstrahlung and Radiological Physics

6. Electron interactions were characterized by a ratio "b/a". The ratio "b/a" represents: a) Orbital electron distance to nuclear radius b) Photon wavelength to atomic radius c) Impact parameter to atomic radius d) Orbital electron radius to nuclear radius 7. The electron-electron interaction that results in brehmsstr

Exposure and the Inverse Square Law

The inverse square law has very practical applications. a) If the exposure at d=30 cm from a point source is 1R, what is the exposure at d=5c from the source? b) Suppose an acceptable chest radiograph was taken using 30mAs at 80kVp from 1m. Suppose that it was now requested that one be taken at 1.5m at 80kVp. What mAs setting

Determining the Alpha Radiation Dose

Please help with the following problem. A particular task exposes the operator to alpha radiation at an average dose of 250 uGy (micro-Gy) each time the task is performed. If the company needs the task performed once per day over a 260-day working year and the maximum occupational dose limit is 20 mSv per year, how many staf

Steady-State Laser Oscillation

Steady-state laser oscillation: (a) The He-Ne laser operates on several s --->p transitions in neon, including the 5s --->3P transition at 632.8 nm. Under the operating conditions of the laser, the fluorescence lifetimes of the upper and lower levels are approximately 100 ns and 10 ns respectively for this transition, and th

Electroatatics and Lighting force.

Please give a brief explanation. B. Where would a positive test charge have the least potential energy? C. How much energy must you add to the system to move 1 electron 1 m in a direction along one of the equal potential lines? D. If lightning strikes a tree 20 m away would you be better to stand facing the tree, your

Body Heat Loss/Caloric Usage

Please help with the following problem. Provide step by step calculations. 1. The average human body has a temperature of 30 degrees celcius, a skin surface are of 1.20mt^2 and an emissivity of 1.0 a. If the surrounding temp is 20degree celcius, the body's net rate of heat loss due to radiation is -------- watts b. How

Polarization and Absorption Energy

Which polarization state of light is transmitted and absorbed (and why) in regular plastic polarizers (which are actually long strings of molecules , imbedded in iodine). Is it true that light with E fields parallel to the molecular strands create acceleration along that direction, which then creates re-radiation; so that the tr

Why is Uranus blue

I know this is because methane absorbs red light but why greenish blue why not bluish green why not some other colour of the spectrum such as violet or orange is this because our eyes are more sensitive to certain colours or because these colours are mixtures with some red in them or another reason

Thermodynamics: Light Bulb

A light bulb has a filament of metal that has an emissivity of 0.3 and a surface area of 5.0 x 10^-5 m^2. It is heated to 2500 degrees Celsius in an environment with a temperature of 25 degrees Celsius. What is the power dissipated through radiation by the filament?

Pocket Ionization Chamber

Pocket ionization chambers are built in the form of an electrical capacitor. You know that capacitance is equal to a change in charge over a change in voltage, as C, where the capacitance, C, is in Farads (F), the voltage, V, is in volts (V) and the charge, Q, is in coulombs (C). You have a chamber that has a sensitive cylin

Gamma Flux and Absorption

A collimated beam of 200 keV gamma radiation delivers an incident energy flux of 2 J m^-2 s^-1 to a lead shield 1 g cm^-2 thick. a. What is the incident photon flux in photons cm^-2 s^-1? b. What is the rate of energy absorption in the shield in both erg g^-1 s^-1, J kg^-1 s^-1 and Gy s^-1

Neutron Absorption

What thickness of cadmium is required to absorb 50% of an incident beam of thermal neutrons? Given: σ_capture = 2550 barns, ρ=8.65 g cm^-3, MW=112.4.

Electron Shielding

You are a radiation scientist working for the space agency. A Mission Coordinator asks you to design shielding to prevent monoenergetic 10 MeV electrons from interacting with a cell culture that is to be flown on an upcoming space shuttle mission. The cell culture is covered with a 1 cm thick sheet of Lucite (density = 1.19 g/cm

Half-Wavelength, etc.

1. Calculate the number of half-wavelengths in a ruby laser operating at a wavelength of 694.3 nm in air, given that the ruby rod, silvered on the ends, is exactly 10.0 cm long. The index of refraction of ruby is 1.69 a. 4.97 billion b. 9.94 billion c. 2.49 billion d. 1.00 billion 2. What is the energy o