1. P6 Wave model of radiation Route map Over the next 12 lessons you will study : Friday 21 October 2011 P6.1 What is a Wave ? P6.2 Describing waves P6.3 Wave properties P6.4 Radiation and waves End of module test P6.5 Bending light beams P6.6 Electromagnetic waves P6.7 Above visible light P6.8 Below the visible light P6.9 Radio waves P6.10 How radio works P6.11 Going digital P6.12 Radiation from space
3. P6.7 Above the visible light Extension questions: 1: State two ways in which UV, X-rays and gamma rays are similar to one another ? 2: The incidence of skin cancer has risen over the last 50 years in the UK as more people holiday abroad. Explain a) what has caused this increase and b) how can we reduce our risk to UV light ? 3: Given one positive benefit or UV light falling on skin cells ? 4: Explain how X-rays can be useful in hospitals? 5: Describe two uses of gamma rays ? Know this: a: Know that UV, X-rays and gamma rays are all ionising radiation B: Know that the higher the frequency of the electro-magnetic wave, the higher the energy of the photon it delivers Friday 21 October 2011 Introduction: The three electromagnetic waves with higher frequency than visible light are UV, X-rays and Gamma rays. Ultraviolet :- UV light is found in sunlight and is emitted by electric arcs and mercury lamps. U.V. is harmful to skin cells, and can cuase skin lesions and cancer. UV light is essential for the production of vitamin D. X-rays :- Has higher frequency and energy than U.V. X-rays are dangerous because they damage living cells deep in the body and can cause cancer. At airports, x-ray machines are used for security checks on baggage. Gamma rays :- come from some radioactive materials. Like x-rays, gamma rays can be used in the treatment of cancer and can be used to kill harmful bacteria and sterilize food and medical equipments. All these waves are ionizing radiation because each photon has enough energy to strip an electron from an atom in its path. In the case of living cells, may damage or destroy them.
4. Key concepts P6.7 a Look at the photograph and information and answer all the questions: How does the a) frequency and b) the wave speed change from radio waves to gamma rays ? Explain what happens to the penetration ability as you move from radio waves to gamma waves ? Doctors exploit the penetrating ability of which wave to examine broken bones ? Electromagnetic waves are transverse waves which travel at a speed of 300,000 kms -1 through a vacuum. This is usually called the speed of light. All e.m waves transfer energy from one place to another and like visible light can be reflected by smooth, hard surface or refracted when they travel form one material to another. through transparent materials. Below visible light
5. P6.7 b Look at the photograph and information and answer all the questions: Exposure to UV-B and UV-B from the sun is the primary cause of skin cancer and responsible for around 80% of cases of melanoma, the most dangerous kind of skin cancer”. New figures out now confirm that skin cancer is the most common form of the disease for females in their twenties. A staggering rate of one malignant melanoma a day is now being diagnosed. Look at the bar chart opposite, explain the tend over the last 10 year sin a) the number of cases of skin cancer and b) deaths from skin cancer ? How can you protect yourself from contracting skin cancer ? UV light is classified into three ranges a) what are they and b) which one is the most harmful and which is the least harmful ? Key concepts
6. P6.7 c Look at the photograph and information and answer all the questions: X-rays are a form of electromagnetic radiation, just like visible light. X-ray machines sends are individual x-ray photons. These pass through the body. A computer or special film is used to record the images that are created. Structures that are dense (such as bone) will block most of the x-ray particles, and will appear white. Why do radiographers, people who use x ray machines protect themselves from regular exposure to x rays ? Name one other use for X rays other than imaging broken bones ? Explain why X-ray photography produce images of the bones in our body but not the flesh ? Key concepts
7. P6.7 d Look at the photograph and information and answer all the questions: In some cancers, cancerous cell are irradiated using a gamma source. The cells are killed by the destructive nature of the gamma radiation. Furthermore, where surgery is impossible, radiotherapy can be used, although the success rate is not high. Killing all the cancerous cells whilst leaving healthy ones intact is very difficult, even for the most skilled surgeons. Explain why not all brain tumours can removed using normal surgical procedures involving a scalpel ? Why would using X rays not work when treating brain cancers ? In the picture below left, the brain tumour is pictured shrinking after successive exposure to gamma rays. Explain why the cancer has shrunk ? Key concepts
8. P6.7 Plenary Lesson summary: UV strike energy visible Friday 21 October 2011 It are that we are put at risk by X rays or gamma rays, but every day and particularly during our summer we are exposed to UV light. These rays can penetrate the first few layers of the skin and later DNAS leading to fatal skin cancer. Sun creams contain metal oxide which act as a barrier and prevent UV (particularly UV-C) radiation form striking our skin. How Science Works: Research about waves found below visible light in the electromagnetic spectrum Preparing for the next lesson: Above _______ light, ionising radiation including ____, X-rays and Gamma rays can alter the materials that they _____. This is because UV, X-rays and Gamma rays have higher frequency than visible light and therefore have higher ___________ than visible light. Decide whether the following statements are true or false : False True 3: The higher the wave’s frequency, the higher the energy the photon delivers ? False True 2: Ultraviolet, X-rays and Gamma rays are all ionizing radiation ? False True 1: Ionizing radiation can damage all living cells ?
10. P6.8 Below the visible light Extension questions: 1: Why are radio waves and microwaves good at transmitting information over long distances ? 2: Infra red has a good heating effect on most objects. Does this mean they are absorbed or reflected by the object ? 3: Write down one use each for infrared, microwaves and radio waves ? 4: Infra cameras can help detected criminals on the run at night. Why do they not use normal cameras ? Know this: a: Know that radio waves, microwaves and Infrared are non ionizing radiation with wavelength less than visible light. b: Know that they can be used to transfer information. Friday 21 October 2011 Introduction: The three kinds of non ionising waves below the visible light are: radio waves; microwaves and infrared. Infrared :- When a radiant heater or grill is switched on, you can detect the infrared radiation coming from it. Most solids absorb infrared, this makes their temperature rise. Grills, toasters, and radiant heaters all use the heating effect of infrared. Microwaves :- Like all electromagnetic waves, microwaves have a heating effect when they are absorbed. This principle is used in microwave ovens, where microwaves penetrate deep into food and heat up the water in it. Radio waves :- Radio waves have the lowest frequencies and largest wavelengths. The are used to send radio signals from one place to another (communications).
11. Key concepts P6.8 a Look at the photograph and information and answer all the questions: How does the a) frequency and b) the wave speed change from radio waves to gamma rays ? Explain what happens to the penetration ability as you move form radio waves to gamma waves ? Doctors exploit the penetrating ability of which wave to examine broken bones ? Electromagnetic waves are transverse waves which travel at a speed of 300,000 kms -1 through a vacuum. This is usually called the speed of light. All e.m waves transfer energy from one place to another and like visible light can be reflected by smooth, hard surface or refracted when they travel form one material to another. through transparent materials. Above visible light
12. P6.8 b Look at the photograph and information and answer all the questions: Radio waves have the longest wavelengths. These waves can be longer than a football field. Radio waves carry signals for your radios and televisions. The antennae on your television set receive the signal, in the form of electromagnetic waves, that is broadcasted from the television station. This is then used to compile a picture with sound. Explain how a radio antenna works ? Does a television work using the same or different technology when compared to a radio ? Bluetooth uses low powered radio waves for wire communication between what type of devices ? radio waves Key concepts
13. P6.8 c Look at the photograph and information and answer all the questions: An energy efficient home uses less energy than a normal home. Saving energy is not just about reducing the amount of heat energy that escapes through the walls, floors, windows and loft space. We can also use energy efficient devices and a bit of common sense, for example turning off lights, boiling less water and wearing warm cloths indoors also saves energy. Look at the thermal image opposite left of a house during the winter months. Which parts of the house allow most heat to escape to the colder surroundings ? Look at the picture opposite left, explain why if you walk between a TV remote and the TV you cannot change channel ? Name three devices found in the kitchen which use infra red to warm or heat food ? Infra red Key concepts
14. P6.8 d Look at the photograph and information and answer all the questions: Microwaves are electromagnetic waves with wavelengths ranging from as long as one meter to as short as one millimetre Microwaves work by shooting tiny waves called microwaves through food. When the microwaves go through the food, they make the water molecules vibrate. This increase the kinetic or heat energy of the food. Heavy uses of mobile phones report a ‘heating effect’ in the left or right ear when using a mobile phone. Does heavy use of mobile phones pose a health risk ? Mobile phones uses microwaves to transmit information from one place to another. List three other uses of microwaves ? Look at the picture above left, it is of a microwave oven. It uses microwaves to heat food. Explain how this happens ? Microwaves and microwave ovens Microwaves used to cook food Key concepts
15. P6.8 Plenary Lesson summary: radio waves microwaves infrared non-ionizing Friday 21 October 2011 A microwave oven uses microwaves to heat food. Microwaves are radio waves. In the case of microwave ovens, the commonly used radio wave frequency is roughly 2,500 megahertz (2.5 gigahertz). Radio waves in this frequency range have an interesting property: They are absorbed by water, fats and sugars. How Science Works: Research into using radio waves, their properties and how they are used to transfer information for use by radios, televisions and Bluetooth used for communications. Preparing for the next lesson: Communication to and from satellites uses ___________ that can pass easily through the atmosphere. _______ _______ are good at transmitting information over long distances. ____________ are good at transmitting information along optical fibres. Radio waves, microwaves and infrared are _____________ radiations. Decide whether the following statements are true or false : False True 3: Radio waves, microwaves and infrared are ionizing radiation ? False True 2: Radio waves has the least frequency of all the electromagnetic waves ? False True 1: All electromagnetic waves can be reflected, refracted, and diffracted ?
17. P6.9 Radio waves Extension questions: 1: Explain the difference between long wave radio and short wave used by TV stations ? 2: Long wave radio has a range of up to 2000 km. Why does long wave radio have such a huge range ? 3: Living near tall building or in a valley can sometimes affect the quality of your TV picture, explain why ? What does interference of waves mean? 4: Explain how Bluetooth works using radio waves and name three devices that use Bluetooth ? Know this: a: Know the proprieties of radio wave and that they are used to transmit information. b: Know that Bluetooth is a system that uses radio waves. To transfer information between mobile phones and other devices without the need for wires. Friday 21 October 2011 Introduction: Radio waves are produced by making an electric current oscillate in a transmitting aerial found on top of a radio or television mast. All radio waves have a lower frequency and longer wavelength than infrared. Radio waves are good at transmitting information over long distances. This is because they don’t get absorbed and they bounce between the Earth’s surface and the ionosphere (part of the atmosphere) The radio waves used for TV and FM radio transmissions have very short wavelengths compared to most radio waves.
18. P6.9 a Look at the photograph and information and answer all the questions: Radio waves have the longest wavelengths in the electromagnetic spectrum. Radio waves do more than just bring music to your radio. They also carry signals for your TV. Using waves with wavelength in excess of 1000 metres means that radio station up to 2000 km can bounce their waves between the Earth’s surface and the ionosphere overcoming the curvature of the Earth Explain why long wave radio is used to broadcast music very long distances ? Look at the dial opposite of a UK long wave radio dial, where is furthest radio station that it can receive using long wave ? Why do aircraft and air traffic controllers communicate by using long wave rather than shortwave ? Key concepts
19. P6.9 b Look at the photograph and information and answer all the questions: Sometimes, effects of diffraction help to receive radio waves in areas located in the "shadow" of obstacles like a tall building in a city. Signals will be weak but readable. If you live in the shadow of a large mountain, there is very little chance that you will receive the medium wave and short waves used by television. Explain how an aeroplane can interfere with radio and television signals ? If you live in the shadow of a hill explain how you can receive a TV or radio signal ? Explain how high rise buildings (opposite left) may affect your TV or radio signal ? Interference of radio and TV signals radio waves reflect from plane direct radio wave Key concepts
20. P6.9 Plenary Lesson summary: frequency wavelength radio waves ionosphere Friday 21 October 2011 RADAR also uses microwaves. The name is shorthand for ‘Radio Detection And Ranging’. Microwave pulses are sent out by a dish aerial and then reflected by an object (such as a plane or a ship). The time it takes for the reflected pulses to come back is measured. From this the distance to the object can be estimated and also its location. How Science Works: Research into how radios work and using AM and FM waves Preparing for the next lesson: ________ waves are produced by making an electric current oscillate in an transmitting aerial. Radio waves have a lower ________ and a longer ___________. Radio waves are reflected by the __________ . Decide whether the following statements are true or false : False True 3: Radio waves have the shortest wavelength and highest frequency ? False True 2: Bluetooth is a system that uses microwaves ? False True 1: The ionosphere is about 100 km from the Earth’s surface ?
22. P6.10 How radio works Extension questions: 1: In an AM radio system, what does ‘modulating the carrier’ mean ? 2: In an FM radio system, what does ‘modulating the carrier’ mean ? 3: What is the advantage of using FM rather than AM ? 4: Explain how you can tell the difference between an AM signal and an FM signal ? 5: Sketch diagrams explaining AM carrier wave and an FM carrier wave ? Know this: a: Know that an AM transmission has changing amplitude but constant frequency, and an FM transmission has changing frequency but constant amplitude. Friday 21 October 2011 Introduction: I nformation that is use by radio, Bluetooth device and TVs is converted first into electrical signals before it is transmitted. This information is then carried on EM waves. There are two ways you can send information as waves – AM and FM. AM radio waves have varying AMPLITUDE . An AM radio transmitter sends out a continuous carrier wave . The signal (e.g. music) is superimposed on the carrier wave using amplitude modulation. FM radio waves have varying FREQUENCY . FM radio (frequency modulation) is exactly the same idea as AM, but instead of changing the carrier wave’s amplitude, you change its frequency.
23. Key concepts P6.10 a Look at the photograph and information and answer all the questions: Explain why you cannot use sound waves to transfer information over long distances ? The diagram above shows a simple radio system. This system uses radio waves will carry sound from one aerial to another. Since radio waves are part of the electromagnetic spectrum they will travel at 300,000 km -1 s. modulator amplifier demodulator amplifier RF carrier AF signal AF signal AF carrier microphone Loudspeaker How a radio works transmitter receiver
24. Key concepts P6.10 b Look at the photograph and information and answer all the questions: Explain why FM radio given better quality sound and b) how does a radio or TV detect the incoming AM or FM waves ? AM and FM waves FM radio works the same way that AM radio works. The difference is in how the carrier wave is modulated, or altered. With AM radio, the amplitude of the signal is varied to incorporate the sound information. With FM, the frequency (the number of times each second that the current changes direction) of the carrier signal is varied. FM signals have a great advantage over AM signals. Both signals are susceptible to slight changes in amplitude. With an AM broadcast, these changes result in static. With an FM broadcast, slight changes in amplitude don't matter RF carrier wave + AF signal AM wave (changing amplitude) RF carrier wave + AF signal FM wave (changing frequency)
25. P6.10 Plenary Lesson summary: frequency carrier amplitude noise Friday 21 October 2011 TV pictures are also transmitted using radio waves. A TV camera scans each scene, breaking it down into hundreds of narrow strips. Information about how the brightness and colour changes along each strip is then used to modulate the carrier an sent out as a wave. How Science Works: Find out about digital and analogue signals and the advantages of using digital signals for communications. Preparing for the next lesson: In Amplitude modulation information is transmitted by varying the _________ of the carrier wave. In Frequency modulation information is transmitted by varying the ________ of the carrier wave. FM are less affected by ___________. The steady stream of waves is called the ______________. Decide whether the following statements are true or false : False True 3: AM waves is less affected by noise than FM waves ? False True 2: FM transmission varies the amplitude of the carrier wave ? False True 1: AM transmission varies the frequency of the carrier wave ?
27. P6.11 Going digital Extension questions: 1: Briefly explain analogue signals and give examples of a device that uses an analogue signal ? 2: Briefly explain what digital signals are and give an example of device that uses a digital signal ? 3: Explain why digital signals are far better quality than analogue ones? 4: Sketch an analogue and a digital signal ? Know this: a: Know that radio, TV, and telephone are all forms of telecommunications – ways of transmitting information long distances. The information may be sounds, pictures, text, or numbers, and it can be sent using wires, radio waves, or light. Friday 21 October 2011 Introduction: Analogue signals vary but Digital signals either On or Off . The amplitude or frequency of an analogue signal vary continuously. An analogue signal can take any value in a particular range. Dimmer switches, thermometers, speedometers and old-fashioned watches are all analogue devices Digital signals can only take two values – they are made up of ‘ pulses ’ : on or off, true or false, 0 or 1 ..... A digital receiver will decode these pulses to get a copy of the original signal. On/off switches and the displays on digital on digital clocks and meters are all digital devices.
28. Key concepts P6.11 a Look at the photograph and information and answer all the questions: Storing music on MP3 players do you think they use digital or analogue ? The diagram above shows how both analogue and digital signals are used to transmit information. In digital systems there is no loss of quality, because the information relies a series of Os and 1s. In analogue noise can occur which cannot be cleaned up. signal analogue signal with noise Analogue verses digital Digital Analogue signal clean digital signal
29. P6.11 b Look at the photograph and information and answer all the questions: 0 2 4 3 0 3 4 3 0 000 010 100 011 000 011 100 011 000 For transmitting information such as sounds and pictures, digital systems have several advantages over analogue ones: Digital signals can be handled by microprocessors (as in computers). Digital signals can carry more information every second than analogue ones. Digital signals can be delivered with no loss of quality. Explain how digital signals advantageous to use than analogue ones ? Explain how digital signals use the binary or base two number system to transmit information ? List three analogue devices and three digital devices ? Analogue to digital 0 1 Key concepts
30. P6.11 Plenary Lesson summary: any two continuously pulses Friday 21 October 2011 A CD (compact disc) contains a metal layer with millions of tiny bumps on it, arranged in a spiral track. When you play a CD, the disc is rotated and laser light is reflected from the bumps. The reflected pulses – the light signals – are turned into electrical signals and then decoded to produce the sound. DVDs (digital versatile discs) use the same idea, although they have to store much information. How Science Works: Research about radiation form space and how information is transmitted through optical fibres. Preparing for the next lesson: The amplitude and frequency of analogue signals vary ____________. An analogue signal can take _______ value in a particular range. Digital signals can only take _________ values, they are made up of ______________. Decide whether the following statements are true or false : False True 3: Analogue signals have better quality the digital ones ? False True 2: Digital signal can carry more information every second than analogue ones ? False True 1: Both digital and analogue signals weaken as they travel ?
32. P6.12 Radiation from space Extension questions: 1: List three EM waves that cannot penetrate the Earth’s atmosphere and why is this a good thing ? 2: List three EM waves that can penetrate the Earths atmosphere ? 3: What is microwave background radiation and what’s its source ? 4: What is a radio telescope and how do they work ? 5: Why do scientist think that Aliens might communicate using a mathematical language (binomial) rather than words ? Know this: a: Know that radio telescopes are mainly used to detect the natural radio waves coming from distant stars and galaxies. They can also be used to search for signals from intelligent extra-terrestrials. Friday 21 October 2011 Introduction: Only some types of electromagnetic wave can pass through the Earth’s atmosphere. Luckily harmful Gamma rays, X-rays and Ultraviolet rays can hardly go through the Earths Atmosphere. Visible light and infra red readily pass through our ozone and atmosphere. The only other large band of radiations that get through the atmosphere is lower-frequency microwaves and UHF and VHF radio waves. Radio telescopes have been developed to detect these frequencies for signs of intelligent life. Imagine one day receiving a broadcast from another life form locate in another solar system ! ? !
33. P6.12 a Look at the photograph and information and answer all the questions: Radio telescopes like those pictured opposite left constantly scan deep space for electromagnetic radio coming form distant stars and far away galaxies. SETI (search for extraterrestrial intelligence) has been funded to look for sign of intelligent life over the last 40 years. So far they have been unsuccessful ! Do you think we will find evidence of extraterrestrial life somewhere in our own galaxy ? Do you think governments should continue to fund scientists who work for SETI ? If we did receive some sort of message would we know where it came form and how long it took to reach us ? How radio telescopes work Key concepts
34. P6.12 b Look at the photograph and information and answer all the questions: As well as observing natural radio emissions from space, radio telescopes can be used to search for extraterrestrial intelligence. The search for these signals is called the SETI project. Astronomers also use telescopes that detect infrared and ultraviolet, but the telescope itself has to be in space, outside the Earth’s atmosphere. What do scientists think background microwave radiation originated from ? Why do scientists use radio telescopes to scan for extraterrestrial life instead of light telescopes ? Do you think that a) intelligent life exists elsewhere and b) will we ever know about this life form considering how vast our own galaxy is ? Radiation from deep space 10 18 Frequency (Hz) 10 7 10 18 Frequency (Hz) 10 7 Light microwave UHF VHF long wave Light microwave UHF VHF long wave Key concepts
35. P6.12 Plenary Lesson summary: microwaves radio waves big bang absorbed Friday 21 October 2011 Radio telescopes are mainly used to detect the radio waves (UHT VHT and long wave) coming from distant stars and galaxies and even planets home to intelligent life forms. Even if we do receive a signal form a life form, our answer may take hundreds even thousands of years to reach the sender due to the vast size of the Universe. How Science Works: Revise for your end of module test. Preparing for the next lesson: ______ waves and __________ are good at transmitting information over long distances. This is because they do not get ___________ by the Earth’s atmosphere as much as most waves in the middle of the EM spectrum or at the high frequency end. Background microwave radiation was created during the ______ _______ . Decide whether the following statements are true or false : False True 3: Satellites dishes are made of metal because metal reflects microwave well ? False True 2: Communication to and from satellites uses microwaves ? False True 1: Radio telescopes are used by astronomers to detect radio waves from space ?