1. Electromagnetic Spectrum

2. Instructions Duration of Lesson: 60 Min
Read through this powerpoint presentation in preparation for the EM wave quiz
You can also use the chapters in your textbook and your notes
Don’t wait until the last minute – prepare your self to avoid stress

3. Introduction Objectives: At the end of the lesson, you will be able to
Describe the main components of the electromagnetic spectrum.
State the properties of ALL EM waves.
Discuss the role of the respective EM waves and some of their applications.

4. What are Electromagnetic Waves ?
If you have ever tuned in to listen to a radio, spoken on a handphone, turned on a light, had an X-ray taken, felt the warmth of sun on your skin.
You have experienced electromagnetic wave

5. Electromagnetic wave Electric field Produced by Simultaneous vibration
Magnetic field
Electric field
Magnetic field

6. Wavelength of Electromagnetic Waves

7. Highest f Lowest f Shortest λ Longest λ
Hence this is the complete EM wave spectrum (the waves below in  ascending order of wavelength; descending order of frequency )
Gamma rays
x-rays
Ultra-violet ray
Visible light
Infra-red ray
Microwave
Radio wave
Highest f
Shortest λ
Lowest f
Longest λ

8. Properties of EM Wave
All electromagnetic waves are transverse wave

9. They do not require any medium to travel through (recall: Radiation Infra red is an EM Wave)
They travel at the speed of 3x108 ms-1 in vacuum (recall: speed of light  light is also an EM Wave)

10. 4. They can all be reflected or refracted

11. 5. They can all be emitted or absorbed by matter

12. Where v = speed of wave (m/s) f = frequency of wave (Hz)
6. They all obey the wave equation
Where v = speed of wave (m/s)
f = frequency of wave (Hz)
λ = wavelength (m)
v =f x λ

13. 7. Their frequencies do not change as they pass from one medium to another. However, both their speed and wavelength will change.
You must know this equation!!
v =f x λ

14. 8. They carry energy frm one place to another
9. They are all of neutral charge as all of them oscillate with electric and magnetic field perpendicular to each other.

15. Electromagnetic Waves Electromagnetic Spectrum
Overview of EM waves
Waves
Longitudinal Waves
Transverse Waves
Sound waves
Electromagnetic Waves
Properties
Classified into
Comprises of
Electromagnetic Spectrum
Radiowave
Infra-Red
Ultra-Violet
Gamma ray
Microwave
Light
X-ray
Applications

16. Gamma rays
Gamma rays have the shortest wavelengths and highest frequencies in the EM spectrum.
It is generated by :
Changes in energy levels in the nucleus
Some radioactive substances and certain nuclear reactions produce gamma rays.
Because of their great penetrating ability, gamma rays can cause serious illness. However when used in controlled conditions, gamma rays is useful in cancer treatment.

17. X-rays X rays is generated by :
Rapid deleceration of fast moving electrons
Changes in energy of innermost orbital electrons
X-rays are used for :
diagnostic tool in dentistry and medicine. Doctors and dentists can examine the condition of a person’s bones, the root of this teeth or the state of other inner part of the body.
Custom officers at airports inspect the content of your luggage using X-rays.
Industry wise, it is used to find cracks in structures just like cracks in bones.

18. Both Gamma rays and X- rays can be detected by:
photographic plates
ionization chamber
phosphorescence

19. Ultra-violet
The main source of ultra-violet radiation is sunlight and it is this radiation which gives rise to suntan and also sunburn.
Ultra-violet radiation is used in hospitals to sterilize the surgical instruments and operating theatres as it kills bacteria and viruses.
UV can be detected by:
Photographic plates
Photoelectric cell
Fluorescence

20. Visible Light
Visible light is the part of the EM spectrum which can be detected by the human eye.
The visible light has its own spectrum which consist of the 7 colours of light :
Red Orange Yellow Green Blue Indigo Violet
An example of visible light is the colourful laser light or the light from a firework.
Some of the uses of light is in
optical fibres in medicine and telecommunications.

21. Infra-red waves Heat can be transferred through infrared radiation.
We often think of infra red as being the same thing as 'heat', because it makes our skin feel warm.
Most of you might have seen infra-red waves in use during the SARS period. (picture on the top right hand corner). It shows a thermo-detector which is placed outside hospitals/airport to identify the warm and cool parts of a person by analyzing infra-red radiation emitted from the person’s body. And through this we can see if someone is having a fever.
Infra red is useful for:
- For navigation through fog & haze as it is less easily scattered compared to visible light
- Medical treatment : to warm injured muscles/sports injuries

22. Microwaves Other uses of microwaves:
One of their most common uses is in microwave ovens. When you switch on a microwave oven , it gives off electromagnetic waves that bounce around inside the oven, penetrating the food. Water molecules in the food absorb the energy from the microwaves, causing the food to get hot.
Other uses of microwaves:
Radar communication (as it is not easily blocked of by buildings/trees)
Analysis of fine details of molecular and atomic structure
Useful demonstration of all wave properties on macroscopic scale
Telephone communication (mobile phones, etc)

23. Radio waves
Radio waves are the electromagnetic waves with the longest wavelengths and lowest frequencies
Like all electromagnetic waves, radio waves can travel through a vacuum. However most of the radio waves we receive have traveled through air. Take the radio as an example. The radio converts the electromagnetic waves into the sound that comes out of the radio speakers.
Uses of radio waves:
Radio and television communication (to transmit sound and picture information over long distance)
Radar & satellite communication
Navigation or ships & aircrafts

24. Electromagnetic Waves Electromagnetic Spectrum
Longitudinal Waves
Transverse Waves
Sound waves
Electromagnetic Waves
Properties
Classified into
Comprises of
Electromagnetic Spectrum
Radiowave
Infra-Red
Ultra-Violet
Gamma ray
Microwave
Light
X-ray
Applications

25. Some tips to help you to remember:
EM Spectrum
Raja’s Mother Is Visiting Uncle Xavier’s Garden
Visible Light Spectrum
Run Off You Girls Boys In View
Radio wave
Micro wave
Infra-red Rays
Visible light
Ultra-violet ray
X-rays
Gamma rays
red
orange
yellow
green
blue
indigo
violet

26. You’ve completed the ELECTROMAGNETIC WAVES lesson
Congratulations!
You’ve completed the ELECTROMAGNETIC WAVES lesson