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Flashcards in Nuclear Physics Deck (16)
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1

What are the relative masses and charges of subatomic particles in the atom?

Protons have relative mass 1, relative charge +1 and are particles.
Neutrons have relative mass, relative charge 0, and are particles.
Electrons have relative mass almost 0, and relative charge -1, and aren't particles. (electrons exist in energy levels around the nucleus).

2

Protons and ____ are equal in number in atoms?

In atoms there are an equal number of protons and electrons, ions are formed when atoms gain/lose electrons.

3

What are atomic and mass numbers?

Atomic number = mass of protons an atom contains. Carbon always has 8.
Mass number = total number of protons and neutrons an atom contains.
Ie -
35 - mass number
Cl
17 - atomic number

4

What are isotopes?

Isotopes are atoms with a different number of neutrons. Hydrogen-3 for instance has a mass number 3 and 1 proton, so it has 2 neutrons.

5

What's radiation?

Radiation is emitted from unstable nuclei of radioactive atoms and is ionising.

6

What is alpha radiation?

Alpha radiation consists of alpha particles identical to the nucleus of a helium atom. When an atom loses alpha radiation, it loses 2 protons and 2 neutrons.
a = 4
He
2

7

What is beta radiation?

High energy electrons are emitted from the nucleus. They form when a neutron splits into a proton and electron and the electron shoots out from the nucleus at high speed.
B = 0
B
-1

8

What's gamma radiation?

Gamma radiation has a short wavelength, high frequency, and is EM radiation which travels a long distance.

9

How penetrating are the types of radiation?

Alpha is least penetrating and can't even pass a hand. It can travel a few cm in air.
Beta is second least, it can penetrate air and paper but is stopped by thin aluminium.
Gamma can only be stopped by several cm of lead or m of concrete.

10

Describe behaviours of the three radiation types in magnetic and electric fields.

Alpha particles are positively charged and so they are deflected in electric fields and magnetic fields and attracted to negatively charged plates.
Beta particles are negatively charged and are attracted to positively charged plates.
Gamma is neutral and passes through.

11

How is radiation detected using photographic film?

Photographic film goes darker when it absorbs radiation. Those working with radiation wear film badges to monitor levels. The photographic film is sealed in thin plastic and lightproof film absorbs the radiation and darkens when developed. The badge contains materials which must be penetrated to reach film: aluminium, copper, lead-tin alloy, plastic. At the centre there's an open area. This monitors radiation levels.

12

How do geiger muller tubes detect radiation?

A geiger-muller tube absorbs radiation and an electric pulse is transmitted to a counting system which detects count rate. The higher the rate, the more radiation.

13

What are background sources of radiation?

Natural:
Cosmic rays from space.
Rocks and soil - radioactive rocks give off radon gas.
Living things - plants absorb radioactive materials and they enter the food chain. This makes up most exposure.
Artificial:
Medical X-Rays/X-Rays from flight.
Radioactive fallout from weapons testing.
Radioactive waste from power stations.

14

Show alpha decay..

219 215 4
Rn -> Po + a
86 84 2
2 protons and 2 protons are lose.

15

Show beta decay...

14 14 0
C -> N + B
6 7 -1
One electron is lost.

16

What's half life?

Nuclei of radioactive atoms are unstable. In radioactive decay they break down and turn into completely different atoms.
Carbon-14 turns to nitrogen-14 when it emits beta radiation. As breakdown occurs, activity in Bq declines.
It's not possible to predict when an atom might decay, but it's possible to measure how long half the nuclei of a radioactive material will take to decay. This is the half-life of the radioactive isotope.