Questions and Answers on Interaction of Radiation with Matter

I try to keep questions submitted by groups as the are. Unclear or trivial questions are not replied. Reply has not been proof read.

Q
Laser
Early and some modern lasers use photons as their primary focus carrier. This is simplified due to the rectilinear propagation of light. However a laser based on a particle that is capable of ionizing particles in its wake could be even more useful. If it could be tailored sufficiently by using particles that easily penetrate certain substances, it could be used only to ionize very specific things, such as calcifications of bones, without leaving a mark on the skin surrounding the bone. Has such a thing ever been done or are there other problems with this idea?
A
I don't understand what you mean by focus carrier. Not all laser beams are ionizing particles. In fact, only X-ray laser has high energy to ionize. Like X-rays, X-ray lasers have very short wavelength.

Laser beam may have a lot of energy because of its intensity, but the photons have long wavelength.

Q
Quality factor
Why do different types of radiation have different quality factors? What makes the radiation more or less dangerous?
A
Quality factor is define in the next module.
Because each type of radiation has its unique properties. They will cause different degree of damage to human health, naturally. Alpha particles deposit most of its energy in a small region, and thus damage is more than that cause by beta particles, which causes less ionization per unit volume.

Q
Photons interaction
With a slight change in energy level (1 or 2 MeV) and we can obtain a different behavior of the electromagnetic radiation (photoelectric effect, Compton effect, and pair production), why is this happening?
A
Photons of different energy have very different properties, including their interaction with matter. Photoelectric effect, Compton effect, and pair production are the only modes of interaction, and the percent of each interaction changes as the energy of the photon varies.

Q
Personal monitoring devices
Personnel in medical and industrial radiography occupations are required to wear radiation-monitoring devices. What types of detectors are they required to wear and how is it regulated?
A
Actually, not all personal monitors are the same. Not long ago, there was a crystal in the monitor device. This crystal records the tracks of ionizing radiations. Using various filters, the dosage may be estimated.
Monitor devices are discussed in the next module.
If you do a search using "personal radiation monitor" AND "nuclear", you will find many sites that are related to nuclear radiation monitors.

Q
Neutron and electrons
What is the interaction between neutrons and electrons due to the magnetic moments present in both particles?
A
Both neutrons and electrons have magnetic moments, but their interaction is very weak. Their interactions do not lead to their detections.

Q
Bremsstrahlung
Is bremsstrahlung radiation (braking radiation) also in the electromagnetic spectrum? If so, does it have a higher or lower frequency than X-ray? How is it similar to X-ray?

Is bremsstrahlung radiation considered as high-energy electromagnetic radiation? Do the photons emitted lose energy mostly by photoelectric effect, Compton effect, or pair production?
A
These rays have wavelengths similar to those of X-rays.

Their interactions are similar to those of X-rays with matter.

Q
Particles enegy
How do particles generally lose their energy in the medium? Does the amount of lost energy equivalent to the radiation measurement?
A
Modes of interactions of various particles have been given in the lectures, and by these modes, particles lose their energy a bit at a time.
Radiation measurements do not measure energy.

Q
Units of radiation energy
What are some of the common units of measure for quantifying a unit of radiation dose? Do any of them directly indicate the significance or amount of biological-based damage caused?
A
Module 11 addresses this question fully.

Q
Eadioactivity and energy
If one has a new sample of a radioactive substance and another old sample (compared to it's half-life) how will their radioactivity measurements differ? Will the older sample only give off fewer particles, or will they be less energetic and register as being weaker on the radiation detector?
A
Radioactivity referrs to the emission of particles, regardless of the energy of the particles. Radioactivity of a sample depends on the number of radioactive nuclei in it. New and old sample may all have very high radioactivity, and low radioactivity. Radioactivity of a sample decreases according to its decay constant (or half life).
Energy and radioactivity are different and unrelated.

Q
Non-ionizing radiation
Are there non-ionizing radiations? Can these be dangerous like ionizing radiations?
A
Radiation includes all the e-m waves such as visible, IR, UV, microwave etc. The ones just mentioned are non-ionizing radiation.