RAD-29

Inverse square

Point-source fluence.

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Radiationinverse square

Governing equation

I=I_1 (d_1/d)^2

where

I_1: At d1 (—)
d_1: d1 (m)
d: d (m)
I: Intensity (—)

Lecture brief

Historical brief

Beer attenuation, Compton (1923), Klein–Nishina, Bragg–Gray cavity and KERMA are the transport of photons and charged particles in matter. The sheets compute fluence, kerma and stopping. This sheet (RAD-29 — Inverse square) is the form associated with inverse square. Working symbols: $I_1$ , $d_1$ , $d$ $\rightarrow$ $I$ . Point-source fluence.

Purpose

Purpose: compute

I

from

I_1

d_1

d

in Radiation physics via

I=I_1 (d_1/d)^2

Point-source fluence. Use it when a real radiation physics question must be answered in SI before a code check.

Live realistic example

In symbols

Live case. Given

I_1 = 1.000\,\mathrm{—}

d_1 = 1.000\,\mathrm{m}

d = 2.000\,\mathrm{m}

, the governing relation

I=I_1 (d_1/d)^2

yields

I = 0.2500\,\mathrm{—}

. Point-source fluence. Move a slider: the numbers are this situation, not a canned story.

Calculator

Inputs

At d1 I_11 —d1 d_11 md d2 m

Outputs

Intensity I0.2500 —

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Narration of this film

Point-source fluence.

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