Question

A patient is given 0.050 mg of technetium-99 m(where m means metastable - an unstable but longlived state), a radioactive isotope with a half-life of about 6.0 hours.

Part A How long until the radioactive isotope decays to 7.8×10−4 mg ? Express your answer using two significant figures. PLEASE FILL THE BLANK! 2. How does a Geiger-Muller counter detect radioactivity? Match the words in the left column to the appropriate blanks in the sentences on the right. Make certain each sentence is complete before submitting your answer. passing through conduct electricity counting detecting instant argon gas liquid electrodes collide with neon gas ionize The Geiger-Muller counter is an----method of ----- radioactivity that is based on the radioactive particle-----a chamber of-----. The radioactive particles------part of the-----, which can then----across----within the chamber.

Answer 1

Part A

Half-life of the radioactive isotope = 6.0hours

Initial concentration of the radioactive isotope = 0.05mg

Final concentration of the radioactive isotope = 7.8 X 10^-4mg

Let 1 be the initial amount present, then the amount of the radioactive isotope remained after a certain time interval, say 'x' is given as 7.8 X 10^-4/ 0.05 = 0.0156.That is the decimal amount remaining after time x is 0.0156mg.

If n is the order of half-lives, then (1/2)ⁿ will be equal to the decimal amount present after the time x.Applying this

(1/2)ⁿ = 0.0156

Taking logarithm on both sides,

n log(0.5)= log(0.0156)

n = log(0.0156)/log(0.5) = -1.8069/-0.3010 = 6.0029 = 6

Hence the time taken for the radioactive isotope to decay to 0.0156 times its initial concentration is given by

6 X 6.0hours = 36 hours

2.Geiger -Muller counter

Fill in the blanks

The Geiger-Muller counter is an instant counting method of detecting radioactivity that is based on the radioactive particle passing through a chamber of neon gas or argon gas. The radioactive particles collide with and ionize part of the neon gas or argon gas, which can then conduct electricity across electrodes within the chamber.