Section 18.4 Detection of Radiation

8/14/2019 Section 18.4 Detection of Radiation

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Manhattan Press (H.K.) Ltd. 1

Section 18.4Section 18.4

Detection of radiationDetection of radiation

Photographic filmPhotographic film

Geiger-Muller counterGeiger-Muller counter


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Detection of radiation

seen

heard

smelt tasted

touched

Radiation cannot be

1. Photographic film

2. Diffusion cloud

chamber

3. Geiger-Muller counter

Methods of detections

18.4 Detection of radiation (SB p. 27)


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Photographic film

Expt. 18E

Blackening of

photographic film

A set-up demonstrates

the blackening effect of

radiation on aphotographic film

sealed

photographic film

key

lifting

tool

sealedradiumsource

http://movie/Expt%2018E/18E.avi


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Photographic film

penetratesthe

wrapping of film

filmblackened

leaving shape of key on

film


cannot penetrate

the metal key

radiation


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consists of two components:

(1) GM tube

(2) scaler

(total no. of counts over a time interval)

orratemeter(no. of counts/second)

Geiger-Muller(GM) counter

Geiger-Muller counter

can measure the amount of radiation



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argon gasmetal wire as

anode (+)

thin mica

window

radiationinsulator

inner wall as

cathode ()

GM tube a metal tube filled with argon gas at low pressure

An electric field is set up

inside by the d.c. voltage

By the action of electric field, the

electron moves towards the anode

By the action of electric field,

the positive ion movestowards the cathode

Electric pulses

produced &

recorded

ionized argon gas

The argon gas is ionized by radiation

Working principle of GM counter


radiation enters


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no. of counts recorded no. of disintegration of /

weak ionizing powerof efficiency of detecting much lower

advantage: only measures intensityof radiation


Detecting of , ,

Advantage / disadvantage

Use of GM counter

disadvantage: cannot distinguish types of radiation


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Class Practice 5:Class Practice 5:A student wants to measure radiation in the following situations.

Match the suitable detector with each of the following situations.

Situation Detector

(a) To test the radiation exposureover one week.

(b) To locate the position of a

building with minimum

radiation intensity.

(c) To count the number of -particles emitted by asource in 5 minutes.

GM tube connected to a scaler

GM tube connected to a ratemeter

Photographic filmAns

wer



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Radiation intake from food

Expt 18FRadiation

intake from

food

Somefood contains

radioactive substances content is low

but accumulate in bodieslong term effect

http://movie/Expt%2018F/18F.avi


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To section 18.5
http://e-ch18_05.ppt/http://e-ch18_05.ppt/

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Section 18.4 Detection of Radiation