Question

If a Gamma source has an average counts/secreading of 160 at 1.0 m at what distance will the reading be at 40counts/sec?

A man with a geiger counter gets a reading of 1000counts per min. above background when he is 0.5 meters away from agamma source. what reading should he expect to get if he a. doubleshis distance from source, b. triples his distance from source, c.halves his distance from source?

Answer 1

Given that, The gamma-souce has a reading of 160 counts/sec (say r₁) at 1 m distance (say d₁).

Key point: As the distance increases, the gamma-source reading decreases.

The distance is inversely proportional to gamma-souce radiation.

i.e. r₁ * d₁ = r₂ * d₂

Here, r₂ = 40 counts/sec, for which, the distance shoud increase.

i.e. 160 * 1 = 40 * d₂

i.e. d2 = 160 / 40 = 4

Hence, the at 4.0 m distance, the gamma-source reading will be 40 counts/sec.

When a man with a geiger counter gets a reading of 1000 counts/min. above background when he is 0.5 meters away from agamma source. The reading, he should he expect to get if he a. doubles his distance from source is 1000/2 = 500 counts/min, b. triples his distance from source is 1000/3 = 333.33 counts/min, c.halves his distance from source is 1000*2 = 2000 counts/min.