SP4f Using Radioactivity

Question 1

Explain how radioactivity is used in irradiating food.

Answer 1

food can be irradiated with gamma rays to kill bacteria, so we can store them for longer and make them safer to eat.

Question 2

Explain how radioactivity is used in sterilising equipment.

Answer 2

instruments are sealed in bags and irradiated with gamma rays to kill micro-organisms.

Question 3

How do smoke detectors work?

Answer 3

they sense the amount of current, and if it falls, the siren sounds.

Question 4

Describe how radioactivity is used in smoke alarms (3)

Answer 4

.α particles ionise air molecules and these ions move across the gap in the detector, forming a current
.when smoke enters the device it sticks to the ions due to the electrostatic force
.this increases their mass thus reduces their speed, which makes the current fall

Question 5

How is radioactivity used in tracing and thickness measuring when a water pipe is leaking?

Answer 5

.a gamma source is used as a tracer, and put into the water
.the GM tube, following the pipe would detect high levels of radiation where water is leaking into the soil

Question 6

Thickness measuring steps (paper is too thick)

Answer 6

.Detector counts the number of β – particles that get through
.The computer senses the number of β – particles getting through, has fallen
.The computer increases the pressure applied to the rollers to make the paper thinner
.Some β – particles are absorbed by the paper
.β – particles are emitted by the source