P4 - Uses of radioisotopes

Question 1

What are tracers used for?

Answer 1

• to detect leaks or blockages in underground pipes
• find the route of underground pipes
• track dispersal of waste
• monitor the uptake of fertilizers in plants
• check for a blockage in a patients blood vessel

Question 2

How does a tracer work?

Answer 2

1) a very small amount of a suitable radioisotope is put into the pipe
2) a detector is passed along the ground above the path of the pipe to track the progress of the isotope
3) an increase in activity is detected in the region of the blockage

Question 3

How do smoke detectors work?

Answer 3

1) the alpha particles hit air particles and ionize them
2) the positive ions and negative electrons move towards the negative and positive plates
3) this creates a tiny current that is detected by electronic circuitry in the smoke alarm
4) some alpha particles hit the smoke particles so less air particles are ionized
5) the smoke detector senses the drop in current and sets off the alarm

Question 4

Where does background radiation come from?

Answer 4

• food
• medical
• radioactivity in air
• rocks
• radiation from space

Question 5

How can the approximate age of a rock sample be found?

Answer 5

By comparing the amounts of uranium and lead present in a rock sample.

Question 6

How is carbon-14 formed?

Answer 6

Cosmic rats enter the Earth’s atmosphere and collide with atoms that release neutrons from their nuclei. The energetic neutrons collude with nitrogen atoms forming carbon-14