Properties of Radiation – Deflection in an electric and magnetic field

An insight into the properties of radiation can be demonstrated by observing their behaviour in a magnetic and electric field.

The animation below shows the deflection of radiation in an electric field.

Alpha Particles in an electric field

Alpha particles are attracted to the negatively charged plate. This confirms that they must be positively charged as unlike charges attract. Alpha particles are helium nuclei; they contain 2 protons which gives them their positive charge.

Beta Particles in an electric field

Beta particles are attracted to the positively charged plate. This confirms that they are negatively charged. Beta particles are fast moving electrons with a very low mass and so have a high charge to mass density. They are deflected much more than the heavier alpha particles.

Gamma rays in an electric field

Gamma rays are unaffected by an electric field. This shows gamma rays are uncharged. Gamma rays are highly energetic waves with no charge associated with them.

The animation below shows the deflection of radiation in a magnetic field.

Alpha particles in a magnetic field

When a charged particle cuts through a magnetic field it experiences a force referred to as the motor effect. Alpha particles are deflected by a magnetic field confirming that they must carry a charge. The direction of deflection which can be determined by Fleming’s left hand rule demonstrates that they must be positively charged. Remember for Fleming’s left hand rule the second finger is aligned with the direction of the current which is from positive to negative.

Beta particles in a magnetic field

Beta particles are deflected by a magnetic field in an opposite direction to alpha particles confirming they must hold a charge opposite to alpha particles. Beta particles are fast moving electrons and are thus negatively charged.

Gamma rays in a magnetic field

Gamma rays are unaffected by a magnetic field. This shows gamma rays are uncharged as they do not experience a force when passing through the lines of a magnetic field. Gamma rays are highly energetic waves with no charge associated with them.