Year 9 Electromagnetic Radiation - For additional resources visit: http://www.iheartscience.net

1. scienceisbeauty.tumblr.com
Electromagnetic Radiation
Sarah Jones

2. Light
• Light is a form of energy known as
electromagnetic radiation.
• Light travels as an electromagnetic wave.
• Light travels through the vacuum of space –
unlike sound.
• It travels at
300 000 km/s
thejetlife.com

3. Wave Motion
• Wave motion is the transfer of energy without
matter.
• Transverse wave e.g. how an ocean wave
travels to the shore while a boat just moves up
and down.
• Longitudinal wave – Sound wave i.e. the
particles that make up the wave move in the
same direction the wave is travelling.

4. http://fabianoefner.com

5. maxresdefault.jpg

6. w3.shorecrest.org

7. Wave Properties
www.schoolphysics.co.uk
www.genesis.net.au

8. • Frequency – number of waves produced each
second (measured in Hz).
• Wavelength (λ) – the distance between two
successive waves (measured in m).
• Amplitude – is the maximum distance a wave
extends beyond its middle position.
www.schoolphysics.co.uk

9. Electromagnetic Radiation
James Maxwell (1831-1879) proposed that a
changing electric field could create a changing
magnetic field – and this would create a
changing electric field – these fields would
continue to generate each other.

10. The changing magnetic field and electric fields
travel through space as transverse waves at right
angles – this is known as an electromagnetic
wave.
mysite.du.edu

11. www2.astro.psu.edu

12. • Electromagnetic radiation includes visible
light, microwaves and x-rays.
• Solar flares on the Sun release large amounts
of energy across the electromagnetic
spectrum.
www.globalspec.com

13. www.nasa.gov

14. www.noaa.gov

15. www.ducksters.com

17. Radio Waves
• Produced by vibrating or oscillating electrons
in a transmitting aerial.
• They can travel large distances.
• Long and short-wave radio signals are used in
communication. www.arairwaves.com

18. FM signal is about 3m wavelengths.
AM signal is about 100m wavelengths.
www.pfnicholls.com

19. • Short-wave radio signals can be transmitted
long distances. The waves are beamed
upwards and are reflected back to earth by
the ionosphere.
• AM radio waves can travel around large
obstacles and travel further than FM,
however, they are lower quality and often
suffer from interference.

20. Microwaves
• Microwaves are absorbed by water, fats and
sugars in foods.
• Microwaves make food molecules vibrate and
heat the food up.
• Glass, paper and plastics don’t absorb
microwaves and metal reflects microwaves.
www.harveynorman.com.au

21. Infrared Radiation
• Heat from the sun is IR.
• IR is close to red light in the visible spectrum
(infra – below, therefore frequency below red
light).
• Objects with a temperature above 0 Kelvin (-
273.15°C) emit IR.
en.wikipedia.org

22. Visible Light
• Light from the Sun is essential for life on Earth.
• Visible light (white light) consists of different
colours – each has a different wavelength and
frequency.
ROY – G – BIV
• Most humans can see all of these wavelengths
(colours) but have the greatest sensitivity to the
green range of the spectrum

24. The Visible Spectrum
• Visible light is a small part of the spectrum
that can be seen by the human eye.
• The wavelengths can be detected by the light-sensitive
cells called rods and cones present in
the eye.

25. Ultraviolet Light
• UV light is radiation with a higher frequency than
violet light (ultra – beyond).
• Sunlight contains UV light.
• You cannot see UV light – it does cause sun burn.
• Many object fluoresce under UV light.
Therefore, they absorb UV light and
emit visible light.
• UV light is used to sterilise objects.

26. Fluorescent minerals under
ultraviolet light

27. X-Rays
• Wilhelm Roentgen discovered x-rays in 1895.
• X-rays can penetrate objects, therefore, they
are useful in finding flaws and checking
structure.
• The high energy of the radiation can damage
cells and tissues
(wear lead shileds).
www.sentara.com

28. Gamma Rays
• Wavelength of about one hundred billionth of
a metre.
• They can only be stopped by thick sheets of
lead or concrete.
• They are produced in the making of nuclear
power.
apod.nasa.gov

29. Medically a patient can be injected with a small
amount of radioactive material that emits
gamma rays – this can then be detected by a
positron emission tomography (PET) scanner.
www.geripal.org

30. The Visible Spectrum

31. Colour
Visible light (white light) consists of different
colours – each has a different wavelength and
frequency.
ROY – G – BIV
The splitting of white light is called dispersion.
cnx.org

32. Objects tend to absorb some wavelengths and
reflect others.

33. The perceived colours under white light, yellowish light, bluish light, and very red light.
practicalpainter.blogspot.com

34. Primary Colours – Red, Green and Blue
Secondary Colours – Magenta, Cyan and Yellow

35. Colour blindness

36. Colour Filters

37. Colour Printing
www.novaprinting.ca

38. Polarisation of Light
physicsnet.co.uk
www.physics.louisville.edu

39. Light Interference