P2 Topic 6

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Which of these is used to help preserve some foods?

  • A. Gamma rays.
  • B. Radio waves.
  • C. Alpha particles.
  • D. Ultrasound waves.

A teacher demonstrates radioactivity to a class. Which of these safety precautions helps most to protect the students during this demonstration?

  • A. Tying long hair back.
  • B. Students washing hands afterwards.
  • C. The teacher controlling the direction of the source.
  • D. Closing the blinds

The emission of a beta-particle is a result of

  • A. Reactive decay
  • B. A chain reaction
  • C. Fusion
  • D. Fission

The radiation from four radioactive sources is aimed at a sheet of cardboard and a 5 cm thick block of aluminium. Johnís teacher uses a detector to discover if any radiation has passed through the materials. Which source emits beta-particles only?

  • A.
  • B.
  • C.
  • D.

Radioactivity was discovered in 1896. This happened because

  • A. Doctors learned how to treat radiation burns.
  • B. The scientist who obtained an unexpected result did not ignore it
  • C. Powerful microscopes were used to see the particles
  • D. Powerful machines were made to produce radioactivity

Johnís teacher showed him a model for half-life in radioactive decay. She used a long tube with a small hole at the bottom. She filled the tube to the 64 ml mark and then opened the tap. John timed how long it took for the water surface to reach other marks. Here are his results. John and Anne discuss whether this is a good model of what happens in radioactive decay. Who is correct?

  • A. John only
  • B. Anne only
  • C. Both John and Anne
  • D. Neither

Measurements of the radiation from a radioactive isotope are uncertain because

  • A. The energy of the particles emitted changes with time
  • B. The half-life of the isotope changes with time
  • C. Background radiation is random
  • D. The energy of the particles must be taken into account

A sample of material contains 60 mg of a radioactive isotope. 6 days later there is only 15 mg of the isotope left. What is the half-life of this isotope?

  • A. 3 days
  • B. 4 days
  • C. 12 days
  • D. 24 days

In 1988, the age of a piece of cloth was measured using radiocarbon dating. The age was said to be 689 Ī 16 years. This means that the cloth was

  • A. Definitely not exactly 689 years old
  • B. Either exactly 673 or exactly 705 years old
  • C. Probably between 673 and 705 years old
  • D. More than 705 or less than 673 years old

Alpha particles are used in smoke detectors because

  • A. They do not burn.
  • B. They are uncharged.
  • C. They emit gamma rays.
  • D. They are strongly ionising.

The activity of a radioactive source changes with time. Which of these shows this change?

  • A.
  • B.
  • C.
  • D.

Compared to a coal-fired power station, using a nuclear power station has the advantage that it

  • A. produces no thermal (heat) energy
  • B. transfers all of the fuel energy into electrical energy
  • C. produces no carbon dioxide
  • D. has a reactor instead of a turbine and generator

In the first few years after its discovery, many scientists died from the effects of radioactivity. This was because

  • A. The scientists did not know the dangers at that time.
  • B. Gamma rays were far more penetrating in those days.
  • C. Safety materials such as lead had not been discovered then.
  • D. Life expectancy was shorter in those days.

Johnís teacher experiments with a radioactive source. Her first measurement is the count rate of the radiation from the source. Then she measures the background count rate. She subtracts the background count rate from the first measurement. Which of the following statements is incorrect?

  • A. Subtracting the background count rate makes the radioactivity more random
  • B. Subtracting the background count rate makes the experiment more valid
  • C. The background count rate is uncertain because radioactive decay is random
  • D. The count rate from the source cannot be accurately predicted because radioactive decay is random

Which of these is a correct description of half-life? Half-life is

  • A. The time it takes half a radioactive atom from the sample to decay
  • B. The time it takes half the radioactive atoms in a sample to decay
  • C. Half the time it takes a radioactive nucleus to decay
  • D. Half the life-time of a radioactive sample

The graphs show how four radioactive substances decay. Which of these substances has the shortest half-life?

  • A.
  • B.
  • C.
  • D.