Dangers of decay

Question 1

Alpha decay dangers (3)

Answer 1

• strongly positive so can easily pull of electrons making
  them strongly ionising
• dangerous inside the body because they can quickly ionise body tissue in a small area causing a lot of damage
• however they cannot penetrate the skin and so are not dangerous out of the body
• produces far more ions/mm than gamma so more damaging in the skin but cannot penetrate the skin

Question 2

Beta decay dangers (3)

Answer 2

• much weaker ionising effect than alpha but longer range in air
• lower mass and charge than alpha particle but a higher speed meaning it can still knock electrons off atoms ionising them
• the weaker ionising effect means it produces fewer ions per mm and so causes much less damage to body tissue

Question 3

Gamma decay dangers (3)

Answer 3

• much weaker ionising effect than alpha or beta because photons carry no charge so do less damage to body tissue which means it can be used in medicine i.e. the treatment of cancerous tumors by damaging cells
• however can lead to side effects such as soreness and infertility
• exposure time is kept to a minimum as well as staff having to use handling tongs to reduce contact

Question 4

Gamma radiation intensity equation and explanation

Answer 4

A gamma source will emit radiation in all directions - it spreads out as you get further away from the source.

Intensity of radiation = radiation energy per second passing normally through unit area = I = k/x^2

n gamma photons/second at distance r
photons pass through an area of 4pi*r^2
I = radiation energy per second / total area = nhf/4pir^2 = k/r^2

Question 5

How to experimentally determine intensity equation

Answer 5

Measuring the intensity at different distances

Question 6

Equipment precaution for people working with radiation

Answer 6

People working with radiation must wear a film badge to monitor their exposure to ionising radiation - contains a film that measures the amount of radiation exposure so when it becomes overexposed, the wearer cannot continue working with the equipment

Question 7

The effect of ionising radiation depends on

Answer 7

the dose recieved and the type of radiation

Question 8

The dose of radiation is measured in terms of the

Answer 8

energy absorbed per unit mass of matter from the radiation

Question 9

Dose equivalent unit

Answer 9

Sieverts (Sv)

Question 10

1Sv =

Answer 10

dose due to 250kV X-rays that would have the same effect

Question 11

Radiation limit per year

Answer 11

15mSv
average is 2mSv
no lower limit below which ionising radiation is harmless - unethical to carry out tests so no evidence

Question 12

Ionising radiation is hazardous because

Answer 12

it can damage living cells

Question 13

How does ionising radiation become damage living cells

Answer 13

• it can destroy cell membranes which causes cells to die or it can damage vital molecules such as DNA directly or indirectly by creating free ions which react with molecules affecting normal cell division and damaging nuclei causing mutations and cancerous tumors.

Question 14

3 ways used to reduce intensity

Answer 14

• No source should contact skin
• Use handling tools to reduce intensity of gamma and so the user is beyond the range of alpha and some beta - particles
• Sealed in lead-lined, thick containers to ensure gas cannot be breathed - in, drunk or splashed on skin and to reduce gamma radiation as well as beta and alpha radiation
• Contact time is kept to as short as possible

Question 15

Ionising effect of radiation can be investigated by using

Answer 15

an ionisation chamber and a picoammeter

Current is proportional to the number of ions per second created in chamber