Question

What is the relationship between MAC & LAC?

If linear attenuation coefficient is m, show that HVL can be written as 0.693/m?

Briefly explain the terms: (i) Excitation (ii) Outer shell ionisation (iii) Inner shell ionisation?

Please answer responses in sentences only (no diagrams). Thanks!

Answer 1

LAC-Linear attenuation coefficient.

This is defined as the amount of energy transferred to the material per unit of track length of particle.

LAC is represented with ( )

S. I unit cm-1

MAC -Mass attenuation coefficient.

This is a measure of the rate of energy loss by a photon beam as it travels through an area of material.

Relationship, between MAC &LAC

MAC=  , Here LAC =

Unit is cm2g-1

HVL is Half value layer it is basically the thickness of any material, in which 50% of the incident energy has been attenuated.

HVL = 0.693/m ( Linear attenuation coefficient)

This relationship comes from Intensity attenuation equation

I =I0 e-mx

0.5 = 1.0 e-mx

It is observed that if the incident energy is 1 and transmitted energy is 0.5 , and x is the thickness of material which is taken as half

So from here, HVL = 0.693/m comes.

Excitation energy - The minimum energy required to change a system from ground state to a particular excited state energy.

Inner shell ionization - There are different shells present in an atom K, L, M, N , different shell have different energy value. The energy required to pull the electron from inner shell. To come out.

Outer shell ionization - The minimum energy required to excite an electron from the outer shell of atom is called outer shell ionization.

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