Duncanrig Secondary School East Kilbride. S2 Physics. Electromagnetic Spectrum. Activity Booklet

Transcription

1 Duncanrig Secondary School East Kilbride Electromagnetic Spectrum Activity Booklet

2 INSTRUCTIONS: Always put today s date and copy carefully each HEADING. Symbols used in this booklet: Copy The little pencil symbol means that you copy the passage neatly into you Physics Jotter. It is important that the Copy Passages are copied accurately since the content may appear in the End of Unit Test on Heat. Read The little book symbol means that you must read the passage carefully so you can extract the required information and so that knowledge is gained for the test. What to do This little symbol means you must collect apparatus and carry out an experiment or follow instructions in an activity. Remember, apparatus may be delicate and costly and should be treated as such. Please return all apparatus to its appropriate place of storage. Questions Answer in sentences This little question symbol means that there are some questions to be answered as best as you can. If you are unsure of an answer, your teacher may help or you can find out the answer from other sources like a text book or internet. More to do The plus sign means that if you have the time there is more work that can be done. SAFETY When carrying out practical work during the Heat unit: ALWAYS FOLLOW INSTRUCTIONS CARRY OUT ACTIVITIES CAREFULLY WEAR SAFETY GOOGLES WHEN REQUIRED LEAVE HOT APPARATUS TO COOL BEFORE CLEARING IT AWAY RETURN EQUIPMENT TO THE CORRECT PLACE Page 2

3 ACTIVITY 1 WHAT IS THE ELECTROMAGNETIC SPECTRUM? READ The electromagnetic spectrum is the complete range of electromagnetic radiation. Electromagnetic radiation travels as a wave and transfers energy from one place to another. The speed in which this radiation travels in air is 300 million metres per second, this can be written as m/s or 3x10 8 m/s. Each type of radiation can be identified by its range of wavelength and frequency. Each type of radiation has its own properties, uses and dangers. The electromagnetic spectrum is split into seven types of radiation: radio waves, microwaves, infrared radiation, visible light, ultraviolet, x-rays and gamma rays. Electromagnetic Spectrum Page 3

4 ACTIVITY 2 TITLE PAGE AND QUESTIONS Using the information and sample title page on page 3 construct you own title page. A title page should contain both text and graphics. Try to include as much information as you can in relation to the electromagnetic spectrum. Use colours where possible. Questions Answer in sentences From the information given in Activity 1 answer the following questions in sentences. 1. What is the electromagnetic Spectrum? 2. How many different types of radiation are in the? 3. List the different types of radiation? 4. How is each type of radiation identified? 5. At what speed does light travel trough air? Page 4

5 ACTIVITY 3 WAVE DEFINITIONS Electromagnetic radiation travels as a wave. Before we can continue studying the electromagnetic spectrum we have to learn about waves. Read Waves A wave is a regular, moving disturbance like waves in a rope or ripples of water in a pond. a wave Energy All waves such as light waves and sound waves carry energy from one place to another. All waves are said to transmit energy. Wave frequency The number of waves which pass a point in one second is called the frequency f. Frequency is measured in hertz, Hz. For example, one hertz is one wave per second. The frequency (f) of a wave is measured by counting the number of waves in a given time and dividing that number by the given time (t) in seconds: frequency = number of waves f= N/t time taken For example, if 10 waves pass a point in 5 seconds: f = N/t f= 10/5 f= 2Hz Page 5

6 Wavelength The distance between two consecutive crests or troughs is the wavelength. The wavelength is given the symbol λ and is measured in metres, m. wavelength wavelength Amplitude The maximum or biggest height of a wave is called its amplitude (A) and it is measured in metres, m, from its rest position. rest position amplitude amplitude Frequency, wavelength and Energy The frequency, wavelength and energy of a wave are all related. Lower frequency waves have longer wavelengths. As there are less waves per second, less energy is transferred. As the frequency of a wave increases, the wavelength gets shorter. As there are more waves per second, more energy is transferred. Page 6

7 Questions Answer in sentences 1. What do waves transfer from one place to another? 2. A Physics Pupil counts 25 water waves reaching the shore in 60 seconds. Calculate the frequency of the water waves? 3. A wave machine generates water waves of a frequency of 5Hz. How many waves would be generated in a minute, in an hour, in a day? 4. A wave diagram is shown below a. what is the wavelength (λ) b. What is the amplitude (A) 5. If this was produced in 1 second, what would be its frequency? 6. Copy and complete the wave diagram below labelling the wavelength, amplitude, crest and trough of wave Page 7

8 ACTIVITY 4 RADIO WAVES Read Radio waves have the longest wavelength of all the types of radiation in the electromagnetic spectrum. As it has the longest wavelength it therefore has the smallest frequency and transfers the least energy. The wavelength of a radio wave can range from 100m (football park) to 0.1m (diameter of a football). Radio waves are invisible to the eye and require an aerial in order to receive them. They are used to send information over long distances. Radio and TV stations broadcast on certain frequencies. All the information (audio & vision) is encoded into the radio wave by the transmitter and is received and decoded by a receiver (radio or television set). Each receiver tunes into a certain frequency of radio wave (channel) and decodes the information from that frequency. Radio and TV stations broadcast signals over a wide range of radio wave frequencies, from 3kHz (kilohertz = 1000 Hz) to MHz (1 megahertz = Hz). Each frequency can be grouped into wavebands. Each waveband has its own advantages and disadvantages. Longer wavelengths (lower frequencies) can travel further as they can bend (diffract) round objects including the curvature of the earth. As they are lower frequency they deliver less information so are unsuitable for high quality sound or television. Page 8

9 Higher frequency stations can carry more information but are limited in the range as they do not diffract. Repeaters are needed to increase the range of the signals. The radio wavebands are shown in a table below Waveband Frequency Wavelength Range Use MF Medium Frequency HF High Frequency VHF Very High Frequency UHF Ultra High Frequency 300 khz to 3 MHz m > 1000 km Local and distant radio broadcasts 3 30 MHz m World wide Long distance communications e.g. ship to shore MHz 10 1m < 1000 km High Quality Short distance FM/Digital Broadcasts m 10cm < 1000 km TV Signals MHz Questions Answer in sentences 1. How does the wavelength of radio wave compare to other forms of radiation in the electromagnetic spectrum? 2. On a car trip from Glasgow to Ayr it is possible to stay tuned to Radio Scotland (810 khz) but Clyde 1 (102.5 MHz) soon loses reception. Why is this? 3. TV Signals are transmitted using UHF (Ultra High Frequency) radio signals. Why is frequency range preferred for TV? 4. In hilly regions satellite and cable are the only way to receive television signals. Why is this? 5. A radio receiver used to be known as a wireless, why do you think this was the case? Page 9

10 ACTIVITY 5 RADIO STATIONS Collect a radio receiver Copy the table below Station Frequency Waveband Clyde 1 Radio Scotland Real Radio Classic FM What to do 1. Use the radio receiver to tune to different stations broadcast on different frequencies and complete the table below. 2. Find two stations of your own and add them to the table Page 10

11 ACTIVITY 6 RADIO TRANSMISSION Read A radio transmitter is required to broadcast information using radio waves. The transmitter will encode the information and transmit the radio wave on a specific frequency. A radio transmitter is a complex electronic system. A simple radio wave transmitter can be made from a file and power supply. This can be used to produce an electrical spark, this spark produces random radio waves of different frequencies, this is called noise and it can interfere with radio broadcasts. Collect a radio receiver, a file, a lab pack and two crock to crock leads, a 1.5V cell, a 4.5V battery. What to do 1. Tune the radio receiver so that it does not pick up any stations. 2. Connect the two leads to the 1.5V cell. 3. Connect one of the leads to the file 4. Gently rub the other lead across the file to produce an electrical spark 5. Listen to radio signal received. 6. Determine the range of the signal. 7. Replace the 1.5V cell with 4.5V battery. 8. Does this effect the range of the signal? 9. Briefly describe the experiment, draw a diagram and describe the signal received. Page 11

12 ACTIVITY 7 RADIO HISTORY 1860 Present day What to do 1. Read the radio history card 2. Collect timeline template and event cards 3. In your working group decide where each event should be placed on the timeline template Page 12

13 ACTIVITY 8 MICROWAVE RADIATION Read Microwave radiation is similar to radio waves but has a shorter wavelength and higher frequency. The wavelength of a microwave is 10cm -> 1cm and its frequency range is 3GHz 30 GHz (1 gigahertz = Hz). Certain frequencies of microwave radiation stimulate water particles and are used in microwave ovens. Other uses of microwave radiation include point to point communications (mobile phones), satellite communication and radar. As microwave radiation is higher frequency than radio waves it travels in straight lines and is able to penetrate the earth s atmosphere. RADAR Radio Detection and Ranging Radar systems use microwaves to detect objects in the sky. Microwaves are transmitted and any reflections from these objects are detected. Using the time it takes for the reflection to be detected and knowing the speed of the microwave in the air ( m/s) the direction and the distance of the object can be calculated. BIG BANG!!!! Physicists argue that cosmic microwaves are from the early stages of the universe and support the Big Bang Theory. Page 13

14 What to do Collect a microwave transmitter, a microwave receiver and a sealed box 1. Your teacher will discuss the law of reflection with you. 2. Setup the apparatus as shown in the diagram. It is important that the transmitter and receiver are placed in correct position following the law of reflection. 3. Place a blank sheet of A4 paper in front of the box. 4. Move the box slowly from A to B and see if you can detect the position of the UHOs (Unidentified Hidden Objects) 5. Mark the position with a pencil 6. Repeat steps 1-4 with a different box 7. Compare the positions with the actual positions of the objects 8. In your jotter write a brief description on how you used your own radar system to find the UHOs. Include a diagram Page 14

15 Questions Answer in sentences 1. How do microwaves differ from radio waves? 2. How is a radar system able to find the direction and distance an object is from radar station? 3. If a microwave from a radar system reflects off a UFO and the time taken for the microwave to return is 0.4s, how far away is the UFO? (Hint what is the speed of microwaves) 4. Mobile phones can cook you brain. What do you think? Page 15

16 ACTIVITY 9 INFRARED RADIATION Read All hot objects give off invisible heat rays called infrared radiation (IR). This part of the electromagnetic spectrum has a frequency that is less than that of visible light. It cannot be seen by the naked eye although you can feel it with your skin. If you are close to a radiator, you cannot see any light emitting from it but you can feel the heat, the heat energy is being transferred in the form of infrared radiation. Uses of Infrared Radiation Services Special cameras called thermal imagers can detect infrared radiation. The use of these cameras is called Thermography and can be used to produce still pictures or videos of infrared radiation. These thermal imagers are used by the fire brigade to find people in smoke filled rooms. These cameras are also used by the police and the army. Page 16

17 Engineering Thermal imagers are used to look at the thermal efficiency of buildings and the reliability of electrical and mechanical components. Infrared radiation emitters are also used in factories to speed up the drying process of paint, glue etc. Medicine In medicine, thermographs of patient s bodies show areas of different temperatures. Doctors have found that malignant tumours are warmer than healthy tissue and show up on thermographs. If people suffer from arthritis then the affected joint will show as a different temperature from a normal joint. Infrared radiation is also used by physiotherapists to treat people with muscle injuries. The infrared radiation penetrates the skin and heats the muscles and tissue. The heat reduces the healing time. Did you know that your TV remote control uses IR signals to communicate with your TV? Page 17

18 Questions Answer in sentences 1. Where does infrared radiation come from? 2. How does the frequency of infrared radiation compare to that of visible light? 3. How does the wavelength of infrared radiation compare to that of visible light? 4. Give examples of the application of infrared radiation in the services, engineering and in medicine. 5. Think of your own example of an application of infrared radiation. Page 18

19 ACTIVITY 10 DETECTING INFRARED RADIATION What to do Collect a Bunsen burner, metal gauze, tongs and an infrared sensor 1. Take a reading from the infrared radiation sensor 2. Using tongs heat a metal gauze in a Bunsen burner until it glows red hot (remember safety goggles) 3. Take it out and let it cool, until the red glow disappears 4. Hold the gauze in front of the radiation sensor. How does the reading change? How does it change when it is brought closer to it? Page 19

20 ACTIVITY 11 DETECTING INFRARED RADIATION 2 Copy the table below Colour Beyond violet Violet Green Red Beyond Red IR meter reading Collect labpack, ray box, prism, an A4 sheet of paper and an infrared detector What to do 1. Use the light source to produce a spectrum on the screen. 2. Move the detector in front of the screen and take readings when it is placed beyond violet, violet, green, red and beyond red. 3. Use the results to draw a bar graph. Page 20

21 ACTIVITY 12 IR WEBCAM AND POSTERS Your teachers may show you a webcam that has been modified to detect Infrared Radiation, some IR posters and a selection of Thermograph images. Your teacher may show you a short video on Long EM Waves Page 21

22 ACTIVITY 13 VISIBLE LIGHT Read Visible light is the only part of the electromagnetic spectrum that we are able to detect with the naked eye. Visible light consists of colours ranging from Red to Violet. Each colour has its own frequency (wavelength). White light consists of all the visible colours. When white light passes through a prism it slows down, if the light enters at an angle it causes the light to bend, this is called refraction. Each colour refracts by a different amount. Higher frequency light (shorter wavelengths) refract more than lower frequency signals (longer wavelengths). What to do Collect a labpack, a ray box, 2 prisms and a sheet of A4 paper, visible spectrum glasses 1. Use the white light source to shine a ray of white light though the prism 2. List the following colours in order from the top down (Violet, red, orange, green, blue, yellow, indigo) 3. Use the second prism to recombine the colour into white light 4. Which light is lowest frequency (refracts the least) which is the highest frequency (refracts the most) 5. Put on your Visible Spectrum Glasses. What colours do you see? Page 22

23 ACTIVITY 14 COLOURS READ Visible light allows us to see the world around us, the shape of objects and the colour of an object. What gives an object its colour? The sun or man made objects such as a light bulb provide a source of white light. White light is made up of different colours, when it hits an object some of the colours get absorbed and some get reflected. What to do Collect a selection of coloured objects, a box, a light source and coloured filters Copy the table Object White Light Blue Light Red Light Green Light 1. Place the different objects in the box 2. List the object in the table and the colour it appears under white light 3. Replace white light with a blue light and list the colour each object appears 4. Repeat with red and green Questions Answer in sentences 1. Why do objects appear different colours under different light sources? 2. Why is it not possible to tell the exact colour of a car under a street light at night? Page 23

24 ACTIVITY 15 SCATTERING OF LIGHT Discuss the following questions in your co-operative groups. Why is the sky blue? Why does the sun change colour, yellow, orange, red? Your teacher will show you a video and a demonstration answering the questions above. Copy and Complete Light from the sun is in colour. White is made up of colours. Some of the light gets by the particles in our atmosphere. As it gets scattered in directions the sky appears. As the blue light is removed from the sun light, the sun appears to be. As the sun sets more light gets scattered making the sun appear. red, white, blue, yellow, scattered, all, light, blue, many Page 24

25 ACTIVITY 16 LASERS READ White light is made up of many different colours. Lasers (Light Amplification by the Stimulated Emission of Radiation) are a source of light that is made up of one colour. It does not spread out so the radiation energy is concentrated on a very small spot. The Laser was invented in the 1960 s, although there was no real application for it. Nowadays Lasers are used in many applications. Science Lasers are used to give very accurate measurements of distance. Both very small distances and very large distances can be measured using a Laser. During the Apollo moon landings reflectors were planted on the moon. Knowing the speed of a laser and the time it takes the laser to reach the moon and back, an accurate measurement of the distance can be made Engineering Lasers can be used to cut, weld, bend, engrave, clean and measure. Their versatility and accuracy means they are found throughout all fields of engineering (mechanical, electrical, civil and chemical). Medicine Lasers are used throughout medicine. Some common uses are laser eye surgery, dermatology (skin), laser scalpels, treatment of tumours, sealing blood vessels and hair removal. Page 25

26 Other uses Lasers can be found everywhere. In the home they are found in DVD, Blue Ray and CD players. There are laser in barcode scanners found in shops. Fibre optic cables that bring broadband communication, telephone and television signals into the home make use of lasers. Your teacher may show you a laser in your classroom Questions Answer in sentences 1. What does the acronym LASER stand for? 2. How is a laser different from light from a light bulb? 3. Lasers are used throughout society, in your opinion what are the top three uses of lasers and why? 4. Can you think of any other uses of lasers? 5. It takes a laser 2.5s to travel from the earth, reflect of the panels on the moon and return. What is the distance between the Earth and the moon? Your teacher may show you a video on the visible spectrum Page 26

27 ACTIVITY 17 ULTRA VIOLET RADIATION Ultraviolet radiation (UV) has a frequency greater than that of visible light (shorter wavelength). It is invisible to the naked eye. As it has a higher frequency than visible light it carries more energy. UV radiation can be split into three types depending on its frequency, UVA, UVB and UVC (UVA has the lowest frequency and UVC has the highest). UV radiation is found in sunlight although 99% of this radiation is blocked by the Earths atmosphere, all UVC is blocked and some of the UVB. Dangers and Benefits Most people are aware of the effects of UV radiation through the painful condition of sunburn. This is caused by over exposure to UV radiation. Too much UV radiation leads to direct DNA damage, sunburn and can also lead to skin cancer. Skin cancer is on the rise in the UK and can be fatal. A little exposure to UVA radiation is however necessary as it helps in the production of vitamin D which is needed to prevent bone disease. Advice on how to reduce the risk of developing skin cancer is available on the Cancer Research UK s SunSmart website What to do Activity 17 a 1. Your teacher will show you a PowerPoint presentation on UV radiation. 2. In your working groups collect a UV Radiation Pack. 3. Read over the information provided in the leaflets and posters. 4. You have a set a UV Statement cards, decide as a group if they are true or false. 5. Now rank your true Statements in order of importance. 6. Your teacher will discuss the findings with the class. Page 27

28 Activity 17 b 1. Read the holiday apartment book giving information about the Ferguson family holiday each year in Tenerife. 2. At the end of the book is a Diary that has been filled in by different members of the family. Use the Holiday Apartment Table and respond to each entry giving advice to the person about UV exposure. 3. Your teacher will discuss the advice given with the class. 4. Using the blank post card write yourself a postcard giving some health advice on UV radiation. Page 28

29 ACTIVITY 18 REDUCING UV EXPOSURE As you have seen in the previous activity the use of sunscreen is advised in the reduction of UV exposure. In this activity we are going to compare two different factors of sunscreen to see which provides the best protection What to do 1. Your teacher will set up the apparatus as shown 2. The UV sensitive beads are placed in the in separate dishes 3. Dish 1 has no sunscreen, dish 2 is coated in factor _ and dish 3 in factor _ 4. The three dishes are placed in the light tight box 5. The UV lamp is switched on for 5 minutes 6. Described the effect the UV radiation had on the beads in dish 1, dish 2 and dish 3 Questions Answer in sentences 1. How does the factor of the sunscreen affect the colour of the beads? 2. What does this tell us? 3. How does sunscreen protect us against over exposure to UV radiation? Page 29

30 ACTIVITY 19 USING UV RADIATION There are dangers involved with over exposure to UV radiation but UV also has advantages and is used in numerous applications in society. Medicine Controlled amounts of UV radiation are used in the treatment of the skin disorders, such as psoriasis and acne. It is also used to treat vitamin D deficiency. Other uses Although UV radiation is invisible, it can cause some fluorescent chemicals to glow and emit visible light. This is put to use in security markings on banknotes, credit cards and food products. Security pens can be used to write security markings on possessions that can only be detected in the presence of UV radiation. Washing powder contains fluorescent chemicals so that clothes appear brighter in the presence of UV radiation in sunlight. What to do Collect a UV lamp and selection of objects that make use of fluorescent chemicals 1. Use a UV lamp to examine each sample 2. Describe what is seen when you place the sample under the UV lamp Questions Answer in Sentences 1. Describe 3 uses of UV radiation in society and why it is used? 2. Why are we able to see certain markings under a UV lamp that are normally invisible? Page 30

31 ACTIVITY 20 X-RAYS IN MEDICINE X-rays are a type of electromagnetic radiation with a frequency greater than ultraviolet (shorter wavelength). As a result x-rays are capable of carrying large amounts of energy. X-rays are invisible to the naked eye but can be detected by photographic film. X-rays are used in medicine to examine the inside of the body. This is done because tissue, muscle and bone all absorb a different amount of x-rays. The x-rays that are not absorbed pass through and develop the photographic plates by different amounts. The areas of plate that are exposed to the most x-rays are darker. So a shadow of your bones or muscles can be achieved. As x-rays carry a large amount of energy, they are dangerous and over-exposure can lead to cancer. Exposure to x-rays is carefully monitored. Radiographers, doctors and any other professionals that use x-rays shield themselves behind lead barriers or leave the room during the x-ray. They also wear a photographic badge that measures the total amount of radiation received. Page 31

32 What to do 1. Collect a selection of x-ray photographs and see if you can determine what it is you are looking at. 2. Copy the table below X-ray Description Number Your teacher will show you a selection of photographic x-rays on a PowerPoint, study them and write a brief description of what you see. Answer in sentences 1. Describe how x-rays can be used to detect a broken bone. 2. Why does a radiographer stand behind lead shielding when an x-ray is taken? 3. Why do you think x-rays have been given this name? Page 32

33 ACTIVITY 21 OTHER USES OF X-RAYS X-rays are used else where in society. In the construction industry welding is a procedure used to fix metal pieces together. Although the weld may look perfect it could still have defects (little gaps) that could weaken it and this could have disastrous consequences. X-rays can be used to study the weld; any cracks in the weld can be detected (similar to a broken bone). Higher frequency x-rays are required as the x-rays have to penetrate metal. X-rays are also used to scan luggage in airports. This allows the airport security to quickly check luggage for anything suspicious in the passenger s luggage. What to do 1. Your teacher may show you a selection of luggage x-rayed at an airport (PowerPoint), which one would you let through? Answer in sentences 1. Industry uses higher frequency x-rays, why is this? 2. Write a brief note on two non-medical uses of x-rays. 3. How do x-rays differ from visible light? Page 33

34 ACTIVITY 22 GAMMA Radiation Gamma radiation has the highest frequency (shortest wavelength) of all types of radiation in the electromagnetic spectrum. As it has the highest frequency, gamma radiation can carry the greatest amount of energy. Dense material such as lead is required to absorb gamma radiation. It can pass easily through the body, damaging cells and as a result requires stringent safety procedures. Safety Procedure 1. Always use forceps to handle a source 2. The radiation window points away from the body 3. Never bring a source close to your eyes 4. A source must be attended by an authorised person (over 16) Gamma rays are produced when a radioactive source (an unstable nucleus) decays and breaks into smaller pieces. Some of the energy is released in the form of gamma rays. The Activity of the radiation, number of decays per second, can be calculated using Activity = number of decays Time in seconds A = N/t The Activity of a radioactive source is measured in Becquerels (Bq). Page 34

35 A Geiger-Muller tube is used to count the number of decays. Questions 1. A Geiger-Muller tube counts 10,000 decays in one minute from a radioactive source. What is the activity of the source? 2. A 1000 decays are measured per day. What is the activity? 3. A radioactive source has an activity 800 Bq. How many counts would be measured in an hour? 4. A radioactive source has an activity of 100Bq, how many decays would occur in a year? 5. The radioactivity of a source is measure over a period of time. Plot a line graph of Activity over time. Time (minutes) Activity (Bq) What happens to the activity over time? 7. How long does it take the activity to half? Page 35

36 ACTIVITY 23 BACKGROUND RADIOACTIVIY What to do Collect a Geiger-Muller Tube and Counter 1. Your teacher will set up the apparatus 2. Switch the counter on for 1 minute and measure the number of counts. 3. Reset the counter and repeat twice more and calculate an average count 4. Calculate the activity (this is called background radiation) 5. Write a brief report and include an explanation on what you found ACTIVITY 24 RADIOACTIVE SOURCES Copy the table Source Count 1 Count 2 Count 3 Average Activity Activity - Background Your teacher will repeat Activity 22 using different radioactive sources. Page 36

37 ACTIVITY 25 USES OF GAMMA RADIATION Gamma Camera In medicine it is important for doctors to study internal organs without surgery. To do this they use a radioactive tracer. A radioactive tracer is used with another chemical to target certain organs. As the chemical passes through the body it emits gamma radiation. The gamma radiation is able to pass through the tissue and is detected by a gamma camera. The radioactive source is specially selected so that it s activity decreases with the correct amount of time, long enough to detect but short enough to reduce any potential damage. Radiation Therapy Cancers are growths of cells that are out of control. Cancerous cells can be treated by drugs, surgery or radiation. The choice of treatment depends on the size and the location of the tumours. Radiation therapy is the process of using gamma radiation to damage the cancer cells to stop them reproducing and shrink the tumour. Radiation can damage healthy cells so a very accurate source of gamma rays has to be used to target the cancer cells and limit the damage done to healthy cells. Industry Radioactive tracers can also be used in industry. These are useful when checking for leaks in pipelines, the gamma rays are able to pass through the steel and concrete and Page 37

38 any leaks can be detected. The activity of the radioactive source has to remain high for a longer period as the pipelines can be very long. Questions 1. Could gamma rays be used to sterilize equipment in hospitals? Explain your answer? 2. Why is lead used to protect us against gamma radiation? 3. Gamma radiation can be used as radioactive tracer what other equipment is needed? 4. Why is gamma radiation useful as a radioactive tracer? 5. A doctor uses a radioactive tracer to check the supply of blood reaching a patients lung. What does the tracer tell us about the diseased lung? What happens to the radioactivity of the tracer over time? Your teacher may show you a short video on Short EM Waves Page 38