P4 - Radiation for life

Sparks

• What happens when two acetate rods are brought near each other?
• What happens when a polythene and a acetate rod are brought near each other?
• Why does an acetate rod become positively charged when rubbed with a duster?
• Suggest how tumble drier sheets can reduce static "cling" in your clothes.

Fission

• What is meant my "enriched uranium" ?
• How does a chain reaction enable a large amount of energy to be produced in the fission of uranium?
• Why is radioactive waste dangerous?
• What do the control rods in a nuclear reactor?

Sparks

• They repel
• They attract
• Electrons move from the acetate rod to the duster.
• The sheets contain oil so they reduce friction; they are made from conducting material so no charge can build up.

Fission

• Uranium contains a greater proportion of the uranium-235 isotope than occurs naturally.
• Extra neutrons are released which split more uranium nuclei producing more neutrons and so on.
• It emits harmful ionising radiation for a long time.
• They absorb some of the neutrons to control the number of fissions occurring.

Uses of electrostatics

• Suggest why a defibrillator must be placed firmly on a patient.
• A defibrillator has a power rating of 100,000W. For how long must it be switched on to provide 500J of energy?
• Ali is spray painting the frame of his bike. Suggest why he will get a better finish if the earths the frame.
• Why do the wired in an electrostatic dust precipitator need to be at a high voltage?

Safe Electricals

• The pd across a resistor is 4V when the current through is 0.5A. What is its resistance?
• Calculate the current in a 10 resistor when the pd across it is 4V.
• Explain how a fuse protects an appliance.
• How does an earth wire stop a person getting an electric shock?

Uses of Electrostatics

• To ensure good electrical contact.
• 5ms
• Electrons flow to or from earth to keep the frame uncharged giving a more even coverage; there is less water; shadows are painted.
• To charge the soot particles when they come near the wires.

Safe Electricals

• 8
• 0.4A
• Wire in a fuse melts if the current becomes too large, breaking the circuit and preventing overheating.
• It is connected to the case of an appliance so that if the case becomes "live," a large current flows in the earth and live wires and the fuse "blows."

Ultrasound

• Body fat is denser than air. In which will ultrasound travel faster?
• Is a Mexican wave a longitudinal or a transverse wave?
• An ultrasound pulse travels 20cm further when it is reflected from one side of the head to the other. How big is the head?
• The time delay for an ultrasound echo in a soft tissue was 0.0004S. At what depth was it reflected if the speed of ultrasound is 1200M/S?

Treatment

• What is "radiotherapy"?
• Give two similarities and two differences between x-rays and gamma rays
• Why is iodine-123 used as a tracer in medicine?
• Explain why gamma radiation is often directed at a tumour from different directions.

Ultrasound

• Body Fat
• Transverse
• 10Cm
• 0.24M

Treatment

• Using radiation to treat diseases such as cancer.
• Both electromagnetic radiation; both have very small wavelength; both very penetrative; both damage or kill living cells.
• Iodine is taken up by the throid gland and it emits only gamma radiation.
• So that the tumour receives the full does of radiation but healthy tissue receives less radiation.

What is Radioactivity?

• Three successive measurements of a radioactive source are different, why?
• The activity of a radioactive sample took 8 hours to decrease from 5000Bq to 1250Bq. What is its half-life?

Uses of Radioisotopes

• Why can't carbon dating be used to find the age of an iron tool?
• Why must a gamma source be used as a tracer rather than alpha or beta?
• Why would you expect a new rock to contain a bigger proportion of uranium to lead than an old rock?
• The half life of carbon-14 is 5600 years. Why can't it be used to date an object believed to be about 100 years old?

What is radioactivity?

• Radioactive decay is a random process.
• 4 hours.

Uses of radio isotopes

• Iron was never living so does not contain any carbon-14
• Only gamma radiation will penetrate through pipes, ground. etc.
• Less uranium has decayed to lead.
• Very little carbon-14 would have decayed so there would be very little change in activity.