P7-radioactivity

Question 1

What are the 3 types of radiation

Answer 1

Alpha radiation
Beta radiation
Gamma radiation

Question 2

Radiation:

Answer 2

release pf energy in the form of moving waves or streams of particles

Question 3

Radioactivity:

Answer 3

A substance that contains stable nuclei that become stable by emitting radiation

Question 4

Geiger counter

Answer 4

Device that lets you measure the number of radioactive elements around you.
(A geiger counter clicks even when it’s NOT near a radioactive source, this effect is due to background radiation, this radiation is from radioactive substances:
In the environment(such as the air)
From space (cosmic rays)
From devices such as x-ray tubes)

Question 5

How did we realise about the structure of a atom the experiments

Answer 5

The plum pudding model(this is the model scientists felt represented the structure of the atom)->Rutherford used positively charged alpha (a) particles to probe atoms in a thin gold metal foil->if the plum pudding model was correct-this is what should have happened, it should have passed through->but some particles deflected back->Rutherford deduced that this must be because there was a positively charged mass in the middle of the atom->Rutherford called this positively charged mass in the middle of the atom-the nucleus

Question 6

What did Rutherford’s experiment show about the structure of an atom and explain how it supports the nuclear model of the atom

Answer 6

Alpha particles are positively charged
The nucleus of an atom is also positively charged
These charges can repel each other changing the direction of the alpha particle
Most of the atom is made of space and so some alpha particles just pass straight through
Rarely some alpha particles hit the nucleus and repel back

Question 7

A “radioisotope” is

Answer 7

Simply an isotope that is radioactive e.g. carbon 14

Question 8

Alpha (a)

Answer 8

An atom decays into a new atom and emits an alpha particle (2protons and neutrons). Alpha radiation is the nucleus of a helium atom travelling at extremely high speed.(the decayed atom has changed into a new element as the number of protons and neutrons has changed into a new element)

Question 9

Beta (B)

Answer 9

An atom decays into atom by changing a neutron into a proton and electron is called a beta particle and high energy fast moving electron is only emitted as the proton stays in the nucleus. (The decayed atom has gained a proton and so has changed into a new element)

Question 10

Gamma radiation (Y)

Answer 10

After alpha or beta particle decay the surplus energy is something emitted. The atom itself is not changed. Gamma radiation is part of the EM spectrum, a wave with a very high frequency, very short wavelength. It emits gamma radiation,it releases energy in the form of electromagnetic radiation

Question 11

When the number of protons and electrons in the atom are equal, scientists say the atom is balanced. Most atoms are stable.
However radioactive atoms

Answer 11

Aren’t they are unbalanced and unstable. They ‘want’ to become stable (balanced). So they try to achieve this state, they emit(give out) energy in the form of radiation

Question 12

Ionising power

Answer 12

Different types of radiations ability to cause other atoms to lose electrons and therefore form ions

Question 13

Alpha has the most ionising power

Answer 13

Has the largest charge so ionises atoms easily as it passes them

Question 14

Beta has less ionising power than alpha but more than beta

Answer 14

Smaller charge, moderately ionises atoms as it passes them

Question 15

Gamma least ionising power

Answer 15

As it doesn’t interact with atoms as much when it passes them

Question 16

Alpha is also the most

Answer 16

Dangerous as it has the greatest ionising power

Question 17

Ionisation

Answer 17

When the radiation from a radioactive substance can knock electrons out of atoms which become charged because they lose electrons

Question 18

Irradiated

Answer 18

When an object is exposed to ionising radiation, but it doesn’t become radioactive

Question 19

Radioactive contamination

Answer 19

Unwanted presence of materials containing radioactive atoms or other materials

Question 20

The hazard from contamination is due

Answer 20

To the decay of the nuclei of the contaminating atoms, the type of radiation emitted affects the level of hazard

Question 21

Workers who use ionising radiation reduce their exposure by

Answer 21

Keeping as far away as possible from the source of radiation (e.g.by using special handling tools with long handles)
Spend as little time as possible in at-risk areas
Shielding themselves by staying behind thick concrete barrier and/or using thick lead plates

Question 22

Radioactive decay is also

Answer 22

Random

Question 23

The activity of a radioactive source=

Answer 23

Number of unstable atoms in the source that decay/sec

Question 24

Count rate=

Answer 24

Number of counts/sec-using a geiger counter

Question 25

Radioactive decay =

Answer 25

Spontaneous process that can’t be controlled and is not affected by temperature. However each radioactive element has its own particular decay rate, which is called the half-life

Question 26

Half life of a radioactive element

Answer 26

The time that it takes half the atoms in a sample to decay-average time taken for the count rate (and so the number of parents atoms) to fall by half is always the same

Question 27

The number of sixes rolled with a fair dice is a

Answer 27

Gd model show random nature of radioactive decay coz can’t predict which dice/atom will ‘decay’ or when. Active sample=less time for the sample to decay (shorter half life).

Question 28

Count rate (number of unstable nuclei)after n half lives=

Answer 28

Initial count rate(number of unstable nuclei)/2^n

n=number of half lives

Question 29

Resolution of an instrument=

Answer 29

Smallest non-zero reading that can be measured

Question 30

Systematic errors

Answer 30

When a measuring instrument consistently reads changes in the quantity to be a scale factor greater or less than the actual change

Question 31

Zero errors

Answer 31

Specific systematic error were the instrument doesn’t read zero when the quantity should be zero

Question 32

Random errors:

Answer 32

An error in a measurement caused by unknown and unpredictable changes in an experiment