O Level Physics Chapter :26: Particles Prepared By: Shakil Raiman.

O Level Physics Chapter :26: Particles

Prepared By: Shakil Raiman

26.1: A Nuclear Atom:

26.1: A Nuclear Atom:

26.2: Alpha Particle Scattering:

Between 1909 and 1911, Geiger and Marsden, students of Lord Rutherford at Manchester University, undertook an experiment in which they aimed an alpha particle source at an extremely thin gold foil.

26.2: Alpha Particle Scattering:

26.2: Alpha Particle Scattering: Alpha particle paths in scattering from gold atoms are shown below. Approximately

1 in 8000 was deflected through more than 90.

26.2: Alpha Particle Scattering:

26.3: Rutherford’s Model of Atom:

26.4.1: Nuclear Reactions: Fission Reaction:

A slow moving neutron is absorbed by U-235 (uranium-235). U-235 splits into two daughter nuclei (barium, Ba-144 and krypton, Kr-89) and three more neutrons and gamma radiation. These three neutrons are absorbed by other three uranium-235 (U-235) and make a chain reaction which is called fission reaction.

Energy is obtained as the Kinetic energy of the products which later produce heat energy.

In nuclear power station, energy is produced due to fission in controlled way.

If the reaction is allowed to take place in an uncontrolled way, the result is a nuclear explosion.

26.4.2: Nuclear Reactions: Fusion Reaction:

In fusion reaction two fast moving nucleus combines together at a very high temperature and pressure and produces energy.

Fusion reaction happens in the stars as very high temperature and pressure is available there..

26.5.1: Electricity Generation:

26.5.2: Electricity Generation: A slow moving neutron is absorbed by U-235 (uranium-235). U-235 splits

into two daughter nuclei (barium, Ba-144 and krypton, Kr-89) and three more neutrons and gamma radiation. These three neutrons are absorbed by other three uranium-235 (U-235) and make a chain reaction which is called fission reaction.

Enriched uranium is used as fuel rod. Graphite is used as moderator. The moderator absorb some of the kinetic

energy of the neutrons to show them down as slow neutrons are easily absorbed by uranium-235.

Control rods are made of boron or cadmium. Control rods absorb the neutrons and take them out of the fission process completely.

Water is pumped in to take out the heat energy from the reactor. Water produces steam and rotate turbine which is connected to generator.

Generator produces electricity.

26.5.3: Use of Control Rod: In normal Operation: Partially inserted or withdrawn into the

core as needed to control the rate of reaction constant or as needed.

In Emergency: Fully inserted to into the core to stop the chain reaction.

26.4: Problem with Disposal of Nuclear Waste:

Nuclear waste is radioactive. The activity is very high Some waste has extremely long half life Needed to be buried deep underground in sealed container. Limited sites for buried deep underground. The site must be impermeable to water and the geology

must be stable which is hard to find.

Thank You All

Wish you all very good luck and excellent result.