A-Level物理-射线Radiation。

Alpha particles

• consists of 2 protons and 2 neutrons (Helium nucleus)
• highly ionizing therefore they strongly attract electrons
• have a charge of +2
• bent by electric and magnetic fields but not as much as beta due to larger mass
• relatively heavy and slow moving
• absorbed by skin / 5cm air / card therefore it has poor penetrating power

Beta Particles

• a fast moving electron
• in beta radiation, a neutron turns into a proton and an electron and the electron is ejected
• very light (little mass)
• weak ionizing ability
• move at 9/10 the speed of light
• bent strongly by electric and magnetic fields
• fast moving, moves up to 30-50cm in air, absorbed by 5mm Al. Can ionize an air molecule

Gamma Rays

• electromagnetic rays
• moves at the speed of light
• high energy radiation with shorter wavelength than X rays
• never fully absorbed therefore has a very long range
• very very weakly ionizing because it has no charge or mass
• not affected by electric and magnetic fields
• kills living cells
• only emitted with alpha and beta particles
• strength halved by thick concrete, thick lead (25mm)

For nuclear equations

• When alpha decay occurs, mass no. decreases by 4 and atomic no. decreases by 2.
• For beta decay, mass number does not change, atomic number increases by 1.
• Gamma decay, a gamma ray is released (energy), no change to mass & atomic number.

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