Electromagnetic Radiation
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scienceisbeauty.tumblr.c Electromagnetic Radiation Sarah Jones
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Year 9 Electromagnetic Radiation - For additional resources visit: http://www.iheartscience.net
Transcript of Electromagnetic Radiation
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Electromagnetic RadiationSarah Jones
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
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.
http://fabianoefner.com
w3.shorecrest.org
Wave Properties
www.schoolphysics.co.uk
www.genesis.net.au
• 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
Electromagnetic RadiationJames 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.
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
www2.astro.psu.edu
• 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
www.noaa.gov
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
FM signal is about 3m wavelengths.AM signal is about 100m wavelengths.
www.pfnicholls.com
• 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.
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
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
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
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.
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.
Fluorescent minerals under ultraviolet light
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
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
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
The Visible Spectrum
ColourVisible light (white light) consists of different colours – each has a different wavelength and frequency.
ROY – G – BIVThe splitting of white light is called dispersion.
cnx.org
Objects tend to absorb some wavelengths and reflect others.
practicalpainter.blogspot.com
The perceived colours under white light, yellowish light, bluish light, and very red light.
Primary Colours – Red, Green and BlueSecondary Colours – Magenta, Cyan and Yellow
Colour blindness
Colour Filters
Colour Printing
www.novaprinting.ca
Polarisation of Light
www.physics.louisville.edu
physicsnet.co.uk
Light Interference
