NUC-18

α range in air

R ≈ 0.31 E^{3/2} cm for α in air at STP (E in MeV). Bragg–Kleeman sketch.

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NuclearBragg–Kleeman

Governing equation

R\approx 0.31\,E^{3/2}\,\mathrm{cm}

where

E: α energy (MeV)
R: Range in air (cm)

Lecture brief

Historical brief

Rutherford, Chadwick, the semi-empirical mass formula, fission (Hahn–Strassmann 1938) and fusion Q-values, then Compton and Bethe–Bloch stopping, are the nuclear toolkit. Decay, binding and dose start here. This sheet (NUC-18 — α range in air) is the form associated with Bragg–Kleeman. Working symbols: $E$ $\rightarrow$ $R$ . Range is the integral of 1/(dE/dx). Alphas of a few MeV stop in centimetres of air.

Purpose

Purpose: compute

R

from

E

in Nuclear physics via

R\approx 0.31\,E^{3/2}\,\mathrm{cm}

R ≈ 0.31 E^{3/2} cm for α in air at STP (E in MeV). Bragg–Kleeman sketch. Use it when a real nuclear physics question must be answered in SI before a code check.

Live realistic example

In symbols

Live case. Given

E = 5.500\,\mathrm{MeV}

, the governing relation

R\approx 0.31\,E^{3/2}\,\mathrm{cm}

yields

R = 4.00\,\mathrm{cm}

. A source, a finite track, a stop. Move a slider: the numbers are this situation, not a canned story.

Calculator

Inputs

α energy E5.5 MeV

Outputs

Range in air R4.00 cm

Reading speed

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Narration of this film

A source, a finite track, a stop.

Range is the integral of 1/(dE/dx). Alphas of a few MeV stop in centimetres of air.

Reading speed

Watch on YouTube