1. Self Study Package Click here to proceed

2. (a) state that all electromagnetic waves are transverse waves that travel with the same speed in vacuum and state the magnitude of this speed (b) describe the main components of the electromagnetic spectrum (c) state examples of the use of the following components: (i) radiowaves (e.g. radio and television communication) (ii) microwaves (e.g. microwave oven and satellite television) (iii) infra-red (e.g. infra-red remote controllers and intruder alarms) (iv) light (e.g. optical fibres for medical uses and telecommunications) (v) ultra-violet (e.g. sunbeds and sterilisation) (vi) X-rays (e.g. radiological and engineering applications) (vii) gamma rays (e.g. medical treatment) (d) describe the effects of absorbing electromagnetic waves, e.g. heating, ionisation and damage to living cells and tissue

3. A wave is a disturbance which transfers energy from one place to another without the transfer of matter A transverse wave is a wave where the wave direction is perpendicular to the direction of vibrations The frequency of a wave is the number of complete waves produced per second The wavelength of a wave is the shortest possible distance between any two points in phase The wave speed is the distance travelled by the wave per second Wave speed = frequency x wavelength or v = f λ

4. You will learn about a specific family of transverse waves This family is called the Electromagnetic Spectrum (or EM Spectrum for short) The waves in this family are called Electromagnetic Waves (or EM Waves for short) As all EM waves are transverse waves, they obey all the wave properties you studied in the previous topic, including the equation v = f λ

5. EM Waves are everywhere around us. and are essential in the functioning and use of modern technology In your syllabus there are 7 components of the EM Spectrum: 7 Components of EM Spectrum Radio Waves Microwaves Infra-red Visible Light Ultra-violet X-rays Gamma Rays Longest Wavelength Shortest Wavelength Lowest Frequency Highest Frequency

6. EM waves can travel through vacuum (i.e. they do not require a medium) Note: They are the only waves in your syllabus which can travel through vacuum The speed of all EM waves is the same in the same medium In vacuum, the speed of EM waves is given the symbol “c”, and this speed is often called “speed of light”. c = 3.0 x 10 8 ms -1 (you need to memorize this number) Important note: even though all EM waves travel at speed c in vacuum, EM waves will slow down when passing through a medium (e.g. light slows down in glass)

7. In your syllabus you are required to memorize the correct sequence of the 7 components of the EM Spectrum There are two helpful tools to help you memorize this 1. Mnemonics of the EM Spectrum (http://minddrills.com/2013/02/08/mnemonic-for- electromagnetic-spectrum-how-to-remember-electromagnetic- spectrum/)http://minddrills.com/2013/02/08/mnemonic-for- electromagnetic-spectrum-how-to-remember-electromagnetic- spectrum/ 2. Electromagnetic Spectrum song (http://www.youtube.com/watch?hl=en- GB&v=bjOGNVH3D4Y&gl=SG)http://www.youtube.com/watch?hl=en- GB&v=bjOGNVH3D4Y&gl=SG You are also required to give examples of how each component of the EM Spectrum is used by humans

8. Radio Waves are used in over-the-air radio and television. They are transmitted from the TV and Radio stations and are picked up by the antennas of radio or television sets. In Singapore, Mediacorp (TV and radio) is broadcasted from Caldecott Hill, SAFRA radio (FM 98.0 and 88.3) is broadcasted from Depot Road and SPH radio (FM 92.0, 91.3 and 100.3) is broadcasted from Toa Payoh. In Singapore, while Mediacorp still broadcasts over-the-air TV, most households receive TV by cable instead of radiowaves.

9. Microwaves are used to cook food in the microwave oven. in communications from and between Satellites (e.g. Global Positioning System (GPS) and Satellite TV) [not in syllabus] Most wireless communications technology also fall under the category of microwaves (e.g. handphones, wireless internet, wireless microphones, etc.)

10. All objects with temperature give out infra-red waves. [Not in syllabus] The hotter the object, the shorter the wavelength of infra-red waves emitted. When an object reaches 500 °C or so, visible light is also emitted. This is how a filament light bulb works. An intruder alarm is designed to detect infra-red waves which correspond to human body temperature Infra-red rays are also used in remote controllers (e.g. for TV and Air-con)

11. You have already studied how visible light behaves in reflection, refraction and through the use of lenses. Recall that visible light is used in the transmission through optical fibres (both for telecommunications as well as for medical endoscopy)

12. UV is sometimes called “black light”, and is often accompanied with a purple glow [not in syllabus] UV rays are required to see hidden features in currency notes as a form of forgery protection (http://www.mas.gov.sg/Currency/Security-Features/How-to- identify-genuine-notes.aspx)http://www.mas.gov.sg/Currency/Security-Features/How-to- identify-genuine-notes.aspx UV is used in sunbeds for artificial tanning Prolonged exposure to UV is harmful to human beings. In fact, UV rays are used for killing bacteria and sterilization of medical and laboratory equipment.

13. X-rays are highly penetrative and is used in medical, security and engineering imaging. Prolonged exposure to X-rays are harmful to humans. This is why when you take a medical X-ray in a hospital, the staff always leave the room while the X- ray is being taken.

14. Gamma Rays are the most highly penetrative and harmful component of the EM Spectrum. Even short exposure to Gamma Rays may kill living tissue. Used in treatment of cancer to kill cancerous cells (e.g. the “gamma knife”)

15. The shorter the wavelength of EM Waves, the more energy the waves carry When more energetic EM Waves are absorbed the following might happen: Heating (e.g. leaving a black object out in the sun causes it to absorb sunlight and heat up) Ionization (atoms and molecules may lose electrons upon absorbing EM Waves and become positively-charged ions) Damage to living tissue and cells

16. EM Waves are transverse waves EM Waves travel at speed of light in a vacuum There are 7 components of the EM Spectrum Absorption of EM Waves may result in heating, ionization or damage to living tissue and cells

17. Click on the link below to do your holiday assignment for the topic of ELECTROMAGNETIC SPECTRUM https://docs.google.com/a/preshigh.edu.sg/forms/d/1215D6 3mmDyjmxxOr0CxK4x5ypoztIbhttXeypJ2iQ4Y/viewform?usp= send_form https://docs.google.com/a/preshigh.edu.sg/forms/d/1215D6 3mmDyjmxxOr0CxK4x5ypoztIbhttXeypJ2iQ4Y/viewform?usp= send_form Deadline: 31 Dec 2014, 11:59pm. Marks will be deducted for late submission. Please note that you also need to complete your assignment for the other topic: SOUND

18. Please attempt the SOUND self-learning package