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### Explore BrainMass

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.

### Nuclear cross-section measurements

1) a. Discuss the concept of a physical hierarchy amongst various cross section measurements. Comment on the overall uncertainties in the various types of cross section measurement techniques.

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

### Explaining Global Warming

How would you explain global warming to a group of elementary students? Thanks.

### 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

### Physics: Why would a deDescrese in ozonecrease in the amount of ozone in the atmosphere increase the likelihood of people getting sunburn?

Why would a decrease in the amount of ozone in the atmosphere increase the likelihood of people getting sunburn? global temperatures would rise. more ultraviolet radiation would reach the ground. they would be exposed to more infrared radiation. the premise is incorrect-ozone and sunburn are not related

### Conceptual E&M question

Hello. I know that for a particle in motion, (let's say a point charge), the electric field generated is given by the Lienard-Wiechert potentials. My problem is as follows. Let's say I have a point charge in motion, and I wanted it to come to rest so that it remains stationary. Would I just set up an Electric field equal

An alternative to shielding of a radiation source is to extend the distance between the radiation source and the worker. The initial design places the worker 1m, from the source. If the design was revised so the worker was 10m from the source, what percentage reduction in radiation exposure would there be for the second position

### Solar Energy: Calculating Incoming Shortwave Radiation

See the attached file. The solar constant is given as: 1.368 kilowatts per square meter (kW/m²) Solar input per unit area averaged over the surface area of the whole Earth is given as: 342 kilowatts per square meter (kW/m²) Planetary albedo is given as 31% Rate per unit area that solar energy is absorbed by Earth's

### Questions on Work Function and KE of Ejected Electrons

Light of wavelength 1900 A is incident on a nickel surface (work function 4.9 eV) a) calculate the stopping potential b) what is the cutoff frequency for nickel? c) what is the threshold wavelength ?

### Colors of planets

Jupiter is more brightly colored than Saturn because Saturn is farther from the sun and colder, making the bands less chemically active and so less colorful. My question is: Does the thickness of the cloud layers have anything to do with the colors?

What do radio waves, infrared radiation, visible light, ultraviolet radiation, X-Rays and gamma rays have in common? How do they differ? Do astronomers look at visible light only? If not, how can they "see" objects in space at other frequencies?

In a certain town the average yearly background radiation consists of 29.4 mrad of X-rays and g rays plus 2.44 mrad of particles having a QF of 9.05. How many mrem will a person receive per year on the average?

### Physics: At what rate does this distant star radiate electromagnetic energy?

A certain star is 15.5 million light-years away from Earth. The intensity of the light that reaches Earth from that star is 6.4e-21 W/m2 (compare this to 1350 W/m2 for the Sun!). At what rate does this distant star radiate electromagnetic energy? Hint: a light-year is the distance that light travels in one year. -The answer i

### Calculating the RMS Electric Field

Calculate the RMS electric field in the sunlight that hits Mars, knowing that the Earth receives about 1360 W/m2 and that Mars is 1.52 times farther away from the Sun (on average) than is the Earth. Please solve and explain problem.

### Ultraviolet and infrared light

We hear people talk of "ultraviolet light" and "infrared light". Why are these terms misleading? Why are we less likely to hear people talk of "radio light" and "X-ray light"?

### Physics: Radiation Intensity Based on Distance

9. An alterative to shielding of the radiation source is to extend the distance between the radiation source and the worker. The initial design places the worker 1m, from the source. If the design was revised so the worker was 10m from the source, what percentage reduction in radiation exposure would there be for the second posi

### Gamma radiation; shielding for control; shielding material

8. A gamma radiation source (226Ra) is used in a hospital laboratory. If shielding is considered as a means of control, how many centimeters are needed to reduce the radiation to 1% of what a worker would be exposed to without shielding? Assume the shielding material is (a) concrete, (b) steel and (c) lead. (Note: You will n

### Physics: Exposure to alpha radiation, how many staff should be assigned to the task?

7. A particular task exposes the operator to alpha radiation at an average dose of 200 &#956;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 20mSv per year, how many staff does the company need to assign to the task?

### Traveling waves are considered.

1) A 100 W lightbulb produces 5.0 W of visible light. (The other 95W are dissipated as heat and infrared radiation.) What is the light intensity on a wall 2.5 m away from the lightbulb? 2)A krypton laser produces a cylindrical red laser beam 2.0mm in diameter with 5.0 W of power. What is the light intensity on a wall 2.5 m aw

### The Size Of The Universe

Assume the universe today is flat with both matter and a cosmological constant but no radiation. a) Compute the horizon of the Universe as a function of Ohm_M and sketch it. (You will need a computer or calculator to do this.) b) What is the current horizon size for a universe with Ohm_M = 1/3 and h =1/sqrt(2)? c) What is

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

### Radiation Pressure in the Sun's Core vs. Gas Pressure

The gas pressure at the center of the sun is 4 x 10^11 atm and the temperature is 2 x 10^7 K. Estimate the radiation pressure and show that it is very small compared to the gas pressure (see attachment).

### Modern Physics and Electromagnetic Wave

The maximum wavelength for which an electromagnetic wave can eject electrons from a platinum surface is 196 nm. When radiation with a wavelength of 141 nm shines on the surface, what is the maximum speed of the ejected electrons?

### 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

### Pressure due to EM radiation

See attached file for full problem description.

### 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

### Why are water and carbon essential to live?

Why are water and carbon essential to live?