Physics radiation topic

Plum Pudding Model 1897

J.J Thomsons model of an atom, in which he thought electrons were randomly distributed within a positively charged sphere

Nuclear Model (Rutherford)

positive charge located in the nucleus (alpha particles) and negative charge spread out evenly outside the nucleus

Niels Bohr (1913)

-electrons move in definite orbits, or energy levels (principal quantum numbers) around the nucleus

-we use this model today to explain the atom's ability to bond with other atoms.

James Chadwick (1932)

Discovered the neutron

Order of discovery of atom

Ancient Greece , plum pudding , nucleus ( Rutherford ) , shells / energy levels , proton , neutron

Rutherford experiment conclusions

1. atom= mostly empty space

2. in order for particle to deflect/bounce back, must be striking positively charged area

3. area must be very small, dense, and contain most of the atom's mass

- most went straight through

- some deflected

- a few reflected

What is radiation?

Particles that are emitted from radioactive materials

radioactive decay

A random process in which unstable nuclei lose energy by emitting radiation

Alpha

2 protons and 2 neutrons also know as helium nucleus

Beta

A fast moving electron

Gamma

electromagnetic wave

Rate of ionising in types of radiation

Alpha = high

Beta= medium

Gamma= weak

Alpha range in air

few cm

Beta range in air

about 1m

Gamma range in air

unlimited

Beta decay occurs when..

A neutron changes into a proton and an electron

Alpha blocked by

paper

Beta blocked by

5mm of aluminium or 2-3mm of lead

gamma blocked by

Several cm of lead and >1m of concrete

activity

The number of radioactive decays per second measured in Becquerels

Half life

The amount of time taken for half of a radioactive sample to decay

Half-Life Calculation

Draw grid

half live / time / activity

alpha symbol

4/2 He or a

Beta symbol

0/-1 e or 0/-1 B

Gamma symbol

0/0 y

Irridation

When an object is exposed to a source of radiation outside the object

contamination

When a radioactive source gets on or in an object

Uses of radiation

smoke detectors, thickness control, sterilizing,

Sterilisation using radiation

Gamma rays used to kill bacteria, extend the life of food

Thickness of metal using radiation

Beta radiation can only pass through low thickness of metal . Measure the amounts of radiation that makes it through the metal to measure the thickness.

Smoke alarms using radiation

An Alpha source inside a smoke alarm ionises the air inside the alarm. Allowing a current to flow

Dangers of radiation

A low dose of radiation can disrupt the DNA contained within cells and cause cancer as the damage cells divide uncontrollably forming a tumour .

A high dose of radiation tends to to kill cells completely, causing radiation sickness

Outside of the body, which radiation is the most dangerous?

beta and gamma- only ones that can penetrate the body, and therefore in to delicate organs

Inside of the body, which radiation is the most dangerous?

alpha sources do all their damage in very localised areas

Ionisation

When an atom loses or gains electrons and becomes charged

Precautions you should take with radiation

- gloves , tongs

- stand behind concrete /lead barriers

- use for short period of time

- keep in lead lined box

peer review

A process by which the procedures and results of an experiment are evaluated by other scientists who are in the same field or who are conducting similar research.

An atom's nucleus can only be stable if

It has a certain amount of neutrons for the amount of protons it has

Geiger-Muller tube

A device that detects radiation . It gives an electrical signal each time radiation it detected the signals can be converted into clicking sounds

Nuclear fission

A nuclear reaction in which a massive nucleus splits into smaller nuclei with the simultaneous release of energy

Where does nuclear fission happen naturally

In cores of stars