Physics- P7: Radioactivity

What is meant when radioactive decay is described as random?

It is impossible to predict when a particular radioactive nucleus will decay as it is spontaneous

What is the piece of equipment called used to investigate radioactivity?

Geiger-Muller counter

What is the plum pudding model?

-Negative electrons embedded in a positively charged sphere

-No protons/neutrons

What is the alpha scattering experiment?

-Alpha particles were fired at a piece of gold foil

-Most went straight through as the atom is mostly empty space

-Some got deflected in different directions as the centre of the atom has a positive charge

-Some bounced straight back as they hit the nucleus so there must be a great deal of mass somewhere

What is an isotope?

Element with a different number of neutrons but the same amount of protons

What would you do to an equation if there is alpha decay?

Take away two neutrons and two protons (from mass, 2 from atomic)

What would you do to an equation if there is beta decay?

Take away a neutron, turns into proton and electron (atomic number increases by 1, mass number stays the same)

Why may neutrons may be emitted by some radioactive substances?

In order to deccay

What is the ionizing power of alpha, beta and gamma particles?

Alpha= high, Beta=middle, Gamma=low

What are alpha, beta and gamma particles stopped by?

-Alpha stopped by paper

-Beta stopped by aluminium

-Gamma stopped by lead

What is the penetration power of alpha, beta and gamma particles?

Gamma=high, beta=middle, alpha=low

What is the range in air alpha, beta and gamma particles?

-Alpha can go a few cm

-Beta can go 1m

-Gamma can go unlimited

How can radiation be used to monitor the thickness of foil?

-Radiation is absorbed as it goes through a beta minus emitter

-If the foil is too thick it the detector receives less beta particles and sends a signal to the rollers to increase force on the foil so it is thinner

-It the foil is too thin the detector receives more beta particles and sends a signal to the rollers to decrease force on foil so it is thicker

How can radiation be used in a smoke alarm?

-Movement of alpha particle is measured against a small gap

-If smoke is detected, it will absorb the alpha particles so the detector will measure a drop in alpha particle detection

-This will cause a sound to go off

What type of radiation is used in a smoke detector?

Alpha

What type of radiation is used to measure thickness monitoring?

Beta

Why is alpha and gamma radiation unsuitable in thickness measuring?

Alpha particles are not penetrating enough, gamma particles are too penetrating

Why is gamma and beta radiation unsuitable in smoke detectors?

They are both too small

What factors are important to consider when determining a radioisotopes use?

-Its half life

-Its penetration power

-Energy of beta emission

What is the difference between irradiation and contamination?

-Irradiation is from beta/gamma sources, contamination is from alpha sources

-Irradiation is exposure, contamination is when its in/on you

What is ionising radiation?

Radiation that has so much energy that it can knock electrons from atoms

Why is ionising radiation dangerous?

-It can cause damage to cells and DNA, possibly causes parts of genetic code to die

-This can cause cancerous growths

How can workers who use ionizing radiation reduce their exposure?

-Standing at a distance to the radiation

-Spending minimal time with the radiation

-Shielding their bodies from the radiation

How can nuclear radiation be used for medical imaging?

-Imaging tests to detect problems in the body

-Images of internal body organs

-Takes images of dense body parts (bones)

How can nuclear radiation be used to destroy cancer cells?

It can ionise the cells and damage their DNA beyond repair so they can’t reproduce and will die

What are the natural sources of background radiation? (with %)

-Radon gas (50%)

-Cosmic rays (10%)

-Food (11%)

What are the man made sources of background radiation? (with %)

-Medical (13%)

-Buildings (15%)

What is nuclear fission?

When an unstable nuclei splits to form 2 smaller nuclei and release energy

What is the difference between spontaneous and induced nuclear fission?

Induced fission is man made and more common whereas spontaneous fission is natural and rarer

What happens in a chain reaction?

Neutrons that are released in fission hit another nucleus to produce at least one additional fission

How can a chain reaction be controlled in a nuclear reactor?

Control rods which can absorb neutrons so they don’t continue to hit nuclei

What would the result be of an uncontrolled chain reaction?

A nuclear explosion

What is nuclear fusion?

When two small, light nuclei collide at high speed to make one heavy nucleus + energy

How does the half life of a radioactive isotope affect the hazard it poses?

The longer the half life, the longer the substance will remain radioactive and therefore the more dangerous it is