A radiation specialist prescribes a dose of 90.0 rem for a patient, using an app

Question

A radiation specialist prescribes a dose of 90.0 rem for a patient, using an apparatus that emits alpha particles.

Part A

How many rads does this dose provide to the patient?

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Part B

How much energy does a 7.00 g sample of irradiated tissue receive?

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Part C

Suppose your hospital has only an electron source available. How many rads should you administer to this patient to achieve the same 90.0 rem dose?

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A radiation specialist prescribes a dose of 90.0 rem for a patient, using an apparatus that emits alpha particles.

Part A

How many rads does this dose provide to the patient?

D =   rad  

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Part B

How much energy does a 7.00 g sample of irradiated tissue receive?

E =   J  

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Part C

Suppose your hospital has only an electron source available. How many rads should you administer to this patient to achieve the same 90.0 rem dose?

D =   rad  

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Explanation / Answer

Part A... A rad is a unit of absorbed dose. A rem is the unit of equivalent dose.
The relation between the two is as follows
equivalent dose = absorbed dose x w_R, where w_R is the radiation weighting factor which depends on the particule and it's energy.

w_R ranges from 1 for x-rays, gamma-rays up to 20 for alphas, heavy nuclei and MeV range neutrons

so , rem = D x w_R

or, D = rem / w_R = 90/20 = 4.5 rad

Part B... The absorbed dose is the energy deposited per kilogram, while the equivalent dose measures the biological damage done.

sample of irradiated tissue = 7.00 gram = 7 x 10^(-3) kg

so, D = energy / sample of irradiated tissue

or, energy = 4.5 rad x 7 x 10^(-3) kg = 0.0315 rad x kg

but 1 rad = 0.01 J/kg

so, energy = 0.0315 rad x kg x 0.01 J/kg = 3.15 x 10^(-4) joule

Part C....D = rem / w_R

here the value of w_R for elctron source is 2

so, D = 90/2 = 45 rad

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