RAD-16

Exposure

X = Q / m_air. 1 R = 2.58×10⁻⁴ C/kg. Charge freed in air.

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DosimetryExposure

Governing equation

X=Q/m,\quad 1\,\mathrm{R}=2.58\times 10^{-4}\,\mathrm{C/kg}

$Q \in \left[0.001, 100\right]$

where

Q: Charge (nC)
m: Air mass (mg)
X: Exposure (C/kg)
X: Roentgen (R)

The figure, part by part

Each numbered marker wears the color of its card. Hover a card to light the marker. Tap a marker to jump to that card. The slider walks a red point along the curve; Animate drawing traces it like a pen.

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①

Governing law — red

X=Q/m,\quad 1\,\mathrm{R}=2.58\times 10^{-4}\,\mathrm{C/kg}

$Q \in \left[0.001, 100\right]$

$Q = 0.001$ $X = 3.88\times 10^{-4}$

Along the curve

②

Domain of the variable — blue

Q_{\min} = 0.001,\quad Q_{\max} = 100

$Q \in \left[0.001, 100\right]$

$Q = 0.001$ $Q = 0.001$

Along the curve

③

Response curve — green

X=Q/m,\quad 1\,\mathrm{R}=2.58\times 10^{-4}\,\mathrm{C/kg}

$Q \in \left[0.001, 100\right]$

$Q = 0.001$ $X = 3.88\times 10^{-4}$

Along the curve

④

Rate of change — amber

\frac{\mathrm{d}X}{\mathrm{d}Q}

$Q \in \left[0.001, 100\right]$

$Q = 0.63$ $X^{\prime} = 0.388$

Along the curve

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-16 — Exposure) is the form associated with Exposure. Working symbols: $Q$ , $m$ $\rightarrow$ $X$ , $X$ . An old photon quantity. Related to air kerma by W/e and (1−g).

Purpose

Purpose: compute

X

X

from

Q

m

in Radiation physics via

X=Q/m,\quad 1\,\mathrm{R}=2.58\times 10^{-4}\,\mathrm{C/kg}

X = Q / m_air. 1 R = 2.58×10⁻⁴ C/kg. Charge freed in air. 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

Q = 2.580\,\mathrm{nC}

m = 10.000\,\mathrm{mg}

, the governing relation

X=Q/m,\quad 1\,\mathrm{R}=2.58\times 10^{-4}\,\mathrm{C/kg}

yields

X = 2.580e-4\,\mathrm{C/kg}

X = 1.000\,\mathrm{R}

. An ion chamber, a collected charge. Move a slider: the numbers are this situation, not a canned story.

Calculator

Inputs

Charge Q2.58 nCAir mass m10 mg

Outputs

Exposure X0.000258 C/kg
Roentgen X1.000 R

Reading speed

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Narration of this film

An ion chamber, a collected charge.

An old photon quantity. Related to air kerma by W/e and (1−g).

Reading speed

Watch on YouTube