15-141214062959-conversion-gate02
DESCRIPTION
Conversion gate 02TRANSCRIPT
15. RadioactivityTeacher notes
This word association activity could be used as a stimulus for either a small-group or whole-class discussion on the advantages and disadvantages of radiation and people’s perceptions of it.
2483.unknown
© Boardworks Ltd 2006
What is ‘radiation’?
The term radiation (also known as nuclear radiation) refers to the particles or waves emitted by radioactive substances.
proton
neutron
electron
An atom has electrons orbiting the outside and a central nucleus, which is made up of protons and neutrons.
Nuclear radiation comes from the nucleus of a radioactive atom.
In a radioactive atom, the nucleus is unstable and so it emits particles or waves to form a more stable atom.
This process is called radioactivity or radioactive decay. It is a natural and completely spontaneous process.
* of 34
How can radiation be detected?
Radiation is all around us – naturally occurring, and man-made sources, but it is invisible, so how do we actually know it’s there?
The effects of radiation can be seen and so it can detected using instruments such as a Geiger-Müller tube.
This is a device that can detect and measure radiation.
Radioactivity can also be detected by the presence of photographic film, which darkens when struck by radiation. This effect led to the initial discovery of radioactivity more than one hundred years ago.
Teacher notes
How a GM tube detects radiation - The tube is filled with Argon gas, and around +400 Volts are applied to the thin wire in the middle. When a particle enters the tube, it pulls an electron from an Argon atom. The electron is attracted to the central wire, and as it rushes towards the wire, the electron will knock other electrons from Argon atoms, causing an "avalanche". Thus one single incoming particle will cause many electrons to arrive at the wire, creating a pulse which can be amplified and counted. This gives us a very sensitive detector.
* of 34
Teacher notes
This five-stage historical sequence tells how the discovery of X-rays led to the discovery of radioactivity.
While viewing the sequence, the importance of building on previous scientific research could be highlighted.
2484.unknown
Teacher notes
This activity, summarising the three types of radiation, could be used to introduce the topic of radiation, as a plenary exercise or as a revision exercise.
2485.unknown
Teacher notes
This virtual experiment illustrates the penetrating power of the three different types of radiation.
It could be highlighted that the GM tube, when switched on, is not at zero. This is because it is reading a small amount of background radiation.
It should also be made clear to the students that they should not put their hands in front of any known radiation source, and that the hand in the experiment is only for illustrative purposes.
2486.unknown
Teacher notes
This activity on the effect of a magnetic field on the three types of radiation could be used as a plenary or revision exercise.
2723.unknown
Description
Ionizing effect
Strongly ionizing
Weakly deflected
2 neutrons, 2 protons
Note:– An alpha particle is the same as a helium nucleus
* of 34
Description
-1
1/1860
Weakly ionizing
Strongly deflected
0
0
Stopped by several centimetres of lead or several metres of concrete
Very weakly ionizing
Teacher notes
This matching activity could be used as a plenary exercise on the penetrating power of radiation. Students could be asked to complete the activity in their books or on mini-whiteboards. The activity could be concluded by completion on the IWB.
2488.unknown
Teacher notes
This matching activity could be used as a plenary exercise on the range in air of the three types of radiation. Students could be asked to complete the activity in their books or on mini-whiteboards. The activity could be concluded by completion on the IWB.
2489.unknown
Teacher notes
This true-or-false activity could be used as a plenary or revision exercise on everyday uses of radiation, or at the start of the lesson to gauge students’ existing knowledge of the subject matter. Coloured traffic light cards (red = false, yellow = don’t know, green = true) could be used to make this a whole-class exercise.
2490.unknown
How can radiation detect a fire?
The alpha particles ionize the air.
If there is smoke present, it interacts with the ions produced by the alpha particles and ionization is reduced.
This means that less current is flowing through the air, which causes the alarm to sound.
α
α
How a smoke alarm works:
The ionization chamber made of two metal plates a small distance apart. One of the plates carries a positive charge, the other a negative charge. Between the two plates, air molecules are ionized by the alpha particles from the radioactive material. The result is positively charged oxygen and nitrogen ions in the air. The free electrons are negatively charged.
The positive ions flow toward the negative plate, as the negative electrons flow toward the positive plate. The movement of the electrons registers as a small but steady flow of current. When smoke enters the ionization chamber, the current is disrupted as the smoke particles attach to the charged ions and restore them to a neutral electrical state. This reduces the flow of electricity between the two plates in the ionization chamber. When the electric current drops below a certain threshold, the alarm is triggered.
* of 34
Teacher notes
This five-stage animation sequence shows how beta radiation is used commercially to help control paper thickness in a paper mill.
2491.unknown
Teacher notes
This four-stage animation sequence shows how beta radiation can also be used to detect the location of cracks in a leaking pipe without having to dig up the whole pipe.
2492.unknown
How can radiation detect cracks?
Gamma rays can also be used to detect cracks after an object has been welded.
If a gamma source is placed on one side of the welded metal, and a photographic film on the other side, any flaws will show up on the film like an X-ray.
Gamma rays are like X-rays.
welded metal pipe
Teacher notes
Image shows radiographic testing of a pipe. The technician is using an X-ray machine to check the pipe for flaws, such as poor welding. The machine (green) sends X-rays through the pipe to radiographic film beneath it (black, taped to the bottom of the pipe). The X-rays are absorbed depending on the thickness and density of the metal, revealing areas that are too thin to be considered safe.
As gamma rays are like x-rays, the technique would be exactly the same if the technician was using a gamma source instead of x-rays.
* of 34
© Boardworks Ltd 2006
Gamma rays are used to kill bacteria, mould and insects in food.
Gamma rays are also used to kill bacteria on medical equipment.
How is radiation used for sterilization?
This can be done even after the food has been packaged. It can affect the taste, but supermarkets like it because it lengthens the shelf life.
It is particularly useful with plastic equipment that would be damaged by heat sterilization.
Photo credit (top right): Gaston Thauvin
Photo credit (bottom left) : Jeff Osborn
* of 34
Teacher notes
This drag and drop activity could be used as a plenary exercise to check students’ knowledge of everyday uses of radiation. Class voting or the use of coloured traffic light cards could make this a whole-class exercise.
2493.unknown
Teacher notes
This six-stage animation sequence shows how radiation has an effect on living tissue, and why it can be so dangerous.
2494.unknown
Teacher notes
This true-or-false activity could be used as a plenary or revision exercise on the dangers of radiation, or at the start of the lesson to gauge students’ existing knowledge of the subject matter. Coloured traffic light cards (red = false, yellow = don’t know, green = true) could be used to make this a whole-class exercise.
2495.unknown
Radiation safety
As well as the normal laboratory safety rules you follow, are there any extra rules concerning radioactivity?
The three types of radiation differ in their effects and physical nature.
All radioactive sources must be handled safely.
The hazard symbol for radiation is shown below:
* of 34
How are radioactive sources used safely?
Radioactive materials could be very dangerous to handle if no safety precautions were taken.
use tongs or a robotic arm to handle radioactive materials.
keep exposure times as short as possible
monitor exposure with a film dose badge
label radioactive sources clearly
wear protective clothing
This is because people and their clothing could become contaminated.
* of 34
Background radiation is the radiation all around us.
How many different sources of background radiation can you think of?
Most of the radioactivity you are exposed to is from natural sources.
Photo credit: © 2006 Jupiterimages Corporation
* of 34
This twelve-stage interactive animation explains more about the sources of background radiation, and how to calculate your annual dose of radiation.
At each stage of the animation, students should keep a running total of each radiation source that affects them, which will give them a final figure at the end of the sequence.
At stage 5: the easiest way to calculate the amount of TV watched per year or time spent on the computer, is to calculate the number of hours spent watching TV or at a computer per day, and then multiply this by 365, which will give an average annual amount.
2496.unknown
© Boardworks Ltd 2006
alpha radiation – Positively charged particles made up of two protons and two neutrons.
background radiation – Constant low-level radiation from food and environmental sources.
beta radiation – High-energy electrons emitted by some radioactive materials.
gamma radiation – Short-wavelength electromagnetic radiation emitted during radioactive decay.
Geiger-Müller tube – A device used to detect and measure radiation from radioactive materials.
ionizing radiation – High-energy radiation capable of ionizing substances through which it passes.
radioactivity – The spontaneous emission of radiation from the nucleus of an unstable atom.
Glossary
Multiple-choice quiz
Teacher notes
This multiple-choice quiz could be used as a plenary activity to assess students’ understanding of radioactivity. The questions can be skipped through without answering by clicking “next”. Students could be asked to complete the questions in their books and the activity could be concluded by the completion on the IWB.
2498.unknown
This word association activity could be used as a stimulus for either a small-group or whole-class discussion on the advantages and disadvantages of radiation and people’s perceptions of it.
2483.unknown
© Boardworks Ltd 2006
What is ‘radiation’?
The term radiation (also known as nuclear radiation) refers to the particles or waves emitted by radioactive substances.
proton
neutron
electron
An atom has electrons orbiting the outside and a central nucleus, which is made up of protons and neutrons.
Nuclear radiation comes from the nucleus of a radioactive atom.
In a radioactive atom, the nucleus is unstable and so it emits particles or waves to form a more stable atom.
This process is called radioactivity or radioactive decay. It is a natural and completely spontaneous process.
* of 34
How can radiation be detected?
Radiation is all around us – naturally occurring, and man-made sources, but it is invisible, so how do we actually know it’s there?
The effects of radiation can be seen and so it can detected using instruments such as a Geiger-Müller tube.
This is a device that can detect and measure radiation.
Radioactivity can also be detected by the presence of photographic film, which darkens when struck by radiation. This effect led to the initial discovery of radioactivity more than one hundred years ago.
Teacher notes
How a GM tube detects radiation - The tube is filled with Argon gas, and around +400 Volts are applied to the thin wire in the middle. When a particle enters the tube, it pulls an electron from an Argon atom. The electron is attracted to the central wire, and as it rushes towards the wire, the electron will knock other electrons from Argon atoms, causing an "avalanche". Thus one single incoming particle will cause many electrons to arrive at the wire, creating a pulse which can be amplified and counted. This gives us a very sensitive detector.
* of 34
Teacher notes
This five-stage historical sequence tells how the discovery of X-rays led to the discovery of radioactivity.
While viewing the sequence, the importance of building on previous scientific research could be highlighted.
2484.unknown
Teacher notes
This activity, summarising the three types of radiation, could be used to introduce the topic of radiation, as a plenary exercise or as a revision exercise.
2485.unknown
Teacher notes
This virtual experiment illustrates the penetrating power of the three different types of radiation.
It could be highlighted that the GM tube, when switched on, is not at zero. This is because it is reading a small amount of background radiation.
It should also be made clear to the students that they should not put their hands in front of any known radiation source, and that the hand in the experiment is only for illustrative purposes.
2486.unknown
Teacher notes
This activity on the effect of a magnetic field on the three types of radiation could be used as a plenary or revision exercise.
2723.unknown
Description
Ionizing effect
Strongly ionizing
Weakly deflected
2 neutrons, 2 protons
Note:– An alpha particle is the same as a helium nucleus
* of 34
Description
-1
1/1860
Weakly ionizing
Strongly deflected
0
0
Stopped by several centimetres of lead or several metres of concrete
Very weakly ionizing
Teacher notes
This matching activity could be used as a plenary exercise on the penetrating power of radiation. Students could be asked to complete the activity in their books or on mini-whiteboards. The activity could be concluded by completion on the IWB.
2488.unknown
Teacher notes
This matching activity could be used as a plenary exercise on the range in air of the three types of radiation. Students could be asked to complete the activity in their books or on mini-whiteboards. The activity could be concluded by completion on the IWB.
2489.unknown
Teacher notes
This true-or-false activity could be used as a plenary or revision exercise on everyday uses of radiation, or at the start of the lesson to gauge students’ existing knowledge of the subject matter. Coloured traffic light cards (red = false, yellow = don’t know, green = true) could be used to make this a whole-class exercise.
2490.unknown
How can radiation detect a fire?
The alpha particles ionize the air.
If there is smoke present, it interacts with the ions produced by the alpha particles and ionization is reduced.
This means that less current is flowing through the air, which causes the alarm to sound.
α
α
How a smoke alarm works:
The ionization chamber made of two metal plates a small distance apart. One of the plates carries a positive charge, the other a negative charge. Between the two plates, air molecules are ionized by the alpha particles from the radioactive material. The result is positively charged oxygen and nitrogen ions in the air. The free electrons are negatively charged.
The positive ions flow toward the negative plate, as the negative electrons flow toward the positive plate. The movement of the electrons registers as a small but steady flow of current. When smoke enters the ionization chamber, the current is disrupted as the smoke particles attach to the charged ions and restore them to a neutral electrical state. This reduces the flow of electricity between the two plates in the ionization chamber. When the electric current drops below a certain threshold, the alarm is triggered.
* of 34
Teacher notes
This five-stage animation sequence shows how beta radiation is used commercially to help control paper thickness in a paper mill.
2491.unknown
Teacher notes
This four-stage animation sequence shows how beta radiation can also be used to detect the location of cracks in a leaking pipe without having to dig up the whole pipe.
2492.unknown
How can radiation detect cracks?
Gamma rays can also be used to detect cracks after an object has been welded.
If a gamma source is placed on one side of the welded metal, and a photographic film on the other side, any flaws will show up on the film like an X-ray.
Gamma rays are like X-rays.
welded metal pipe
Teacher notes
Image shows radiographic testing of a pipe. The technician is using an X-ray machine to check the pipe for flaws, such as poor welding. The machine (green) sends X-rays through the pipe to radiographic film beneath it (black, taped to the bottom of the pipe). The X-rays are absorbed depending on the thickness and density of the metal, revealing areas that are too thin to be considered safe.
As gamma rays are like x-rays, the technique would be exactly the same if the technician was using a gamma source instead of x-rays.
* of 34
© Boardworks Ltd 2006
Gamma rays are used to kill bacteria, mould and insects in food.
Gamma rays are also used to kill bacteria on medical equipment.
How is radiation used for sterilization?
This can be done even after the food has been packaged. It can affect the taste, but supermarkets like it because it lengthens the shelf life.
It is particularly useful with plastic equipment that would be damaged by heat sterilization.
Photo credit (top right): Gaston Thauvin
Photo credit (bottom left) : Jeff Osborn
* of 34
Teacher notes
This drag and drop activity could be used as a plenary exercise to check students’ knowledge of everyday uses of radiation. Class voting or the use of coloured traffic light cards could make this a whole-class exercise.
2493.unknown
Teacher notes
This six-stage animation sequence shows how radiation has an effect on living tissue, and why it can be so dangerous.
2494.unknown
Teacher notes
This true-or-false activity could be used as a plenary or revision exercise on the dangers of radiation, or at the start of the lesson to gauge students’ existing knowledge of the subject matter. Coloured traffic light cards (red = false, yellow = don’t know, green = true) could be used to make this a whole-class exercise.
2495.unknown
Radiation safety
As well as the normal laboratory safety rules you follow, are there any extra rules concerning radioactivity?
The three types of radiation differ in their effects and physical nature.
All radioactive sources must be handled safely.
The hazard symbol for radiation is shown below:
* of 34
How are radioactive sources used safely?
Radioactive materials could be very dangerous to handle if no safety precautions were taken.
use tongs or a robotic arm to handle radioactive materials.
keep exposure times as short as possible
monitor exposure with a film dose badge
label radioactive sources clearly
wear protective clothing
This is because people and their clothing could become contaminated.
* of 34
Background radiation is the radiation all around us.
How many different sources of background radiation can you think of?
Most of the radioactivity you are exposed to is from natural sources.
Photo credit: © 2006 Jupiterimages Corporation
* of 34
This twelve-stage interactive animation explains more about the sources of background radiation, and how to calculate your annual dose of radiation.
At each stage of the animation, students should keep a running total of each radiation source that affects them, which will give them a final figure at the end of the sequence.
At stage 5: the easiest way to calculate the amount of TV watched per year or time spent on the computer, is to calculate the number of hours spent watching TV or at a computer per day, and then multiply this by 365, which will give an average annual amount.
2496.unknown
© Boardworks Ltd 2006
alpha radiation – Positively charged particles made up of two protons and two neutrons.
background radiation – Constant low-level radiation from food and environmental sources.
beta radiation – High-energy electrons emitted by some radioactive materials.
gamma radiation – Short-wavelength electromagnetic radiation emitted during radioactive decay.
Geiger-Müller tube – A device used to detect and measure radiation from radioactive materials.
ionizing radiation – High-energy radiation capable of ionizing substances through which it passes.
radioactivity – The spontaneous emission of radiation from the nucleus of an unstable atom.
Glossary
Multiple-choice quiz
Teacher notes
This multiple-choice quiz could be used as a plenary activity to assess students’ understanding of radioactivity. The questions can be skipped through without answering by clicking “next”. Students could be asked to complete the questions in their books and the activity could be concluded by the completion on the IWB.
2498.unknown