Question

Explain why there might be discrepancies for the different types of radiation if graphed in the same manner as your count rate versusinverse square of the distance graph. What type of radiation would you imagine having the most discrepancy?

Answer 1

The type of radiation obeying such a law I remember to be the nuclear radiation (radiation from radioactive substances), and is found to consist of up to three different kinds of rays: alpha (), () and gamma () rays.

For a large number of disintegrations, there is a definite average rate of disintegration which is characteristic of a given substance. A raw count rate is calculated from the number of counts in a time period (). The count rate is then obtained by subtracting the background count rate from the raw count rate:

Alpha rays are identical to the nuclei of a helium atom (hence charged at +2e) and are emitted at speeds of ~1/20th the speed of light. Beta rays are high speed electrons whose speed can reach 99% of the speed of light. Gamma rays are electromagnetic radiation with wavelengths somewhat shorter than X-rays.

The absorption of radiation varies with type and its energy. The absorption (inversely the penetrating power) may be given in terms of absorber transparency:

R_a and R_o are the count rates with and without the absorber respectively.

K=absorption coefficient

x=absorber thickness

The constant K depends on the absorber and the kind of radiation incident on it.

Radioactive materials emit radiation uniformly in all directions. If there is no absorption of the radiation as it travels, then the intensity of radiation (number of particles passing through a unit area each second = count rate per area) at distance r:

N=number of particles

The parameters through which these particles can be discriminated are the mass and the energy. The detectors quantify these parameters through the detection medium (medium in which the radiation produces an effect), and the recording system.

Few clasifications exist, but this extends the answer beyond the question.

Now, depends on the experimental set-up.

[The actual particles detected is the intensity of radiation through the area of the detector:

S_d=area of the detector]

OBS:

TO CONCLUDE: IF WE CONSIDER THE RADIATIONS MENTIONED (ALPHA, BETA, GAMMA), ALPHA PARTICLES ARE MORE LIKELY TO SHOW DISCREPANCY IN THE GRAPH. DUE TO THEIR ENERGY (LOWER THAN THAT FOR BETA AND GAMMA), AND MASS-STATIONARY MASS- (MUCH HIGHER THAN THAT FOR BETA AND GAMMA).