This page contains the detailed and easy notes for GCSE EDUQAS Physics Light and EM waves for revision and understanding Light and EM waves .
Waves are oscillations or disturbance that transfer energy from one point to another.
Wave Speed
It is the distance travelled
by the wave each second.
Crest
It is the height of the
wave.
Amplitude
It is the maximum displacement
of the wave from the mean
position.
In the example it is 5 m
Frequency
It is the number of waves
passing each second.
It is measured in Hertz (Hz)
F = 1/T 1/4
=0.25H3
Wavelength
The distance between
two consecutive crests
or trough.
Time Period
The time it takes for one
wave to travel.
In the example, one wave
is completed in 4 second.
Trough
It is the depth of the wave.
Reflection is the phenomenon of bouncing
off the wave when it hits a medium.
eq: Reflection of light wave when it hits a plain
mirror.
LAWS OF REFLECTION
a) Incident ray, reflected ray
and normal are in the same
plane.
b) The angle of incidence
is equal to the angle
of reflection.
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| REAL IMAGE | VIRTUAL IMAGE |
| 1. Image can be obtained on a screen. | 1. Image cannot be obtained on a screen |
| 2. The rays actually meet where the image is formed. | 2. The rays happen to meet where the image is formed. |
| eg Images of the cinema |
The pencil appears to be
broken as the light is
refracted in water.
Visble light is a spectrum of 7 colours VIBGYOR
Each colour has its own freqency and wavelength.
The visible colour of the object will be the colour that is reflected by the object.
Opaque Object
Opaque objects
does not allow the
light to be transmitted
but absorb all
the light.
eg Book,
Translucent Object
These objects
allow some part
of the light to be
transmitted.
eg Plastic
Transparent Object
They allow the
light to be transmitted
through them
without any absorption
eq glass
The speed of the sound wave is 330m/s.
Human hearing range
20 Hz to 20,000 Hz
In Echo sounding, high frequency sound waves are sent to determine
the depth or find any object.
The time taken by the sound to come back is noted for the known speed
of sound.
S = vt/2
It is the frequency of sound greater than 20,000 Hz.
ADVANTAGES
USES
1. Used in prenatal scanning.
2. Used to determine the depth of
the sea or the obstacle inside
3. Industrial Imaging .
4. Detecting flaws in metal castings.
water.
Transducer sends ultrasound waves. It crosses
the body and reflected from the tissues. The Transducer
detects the waves reflected from the tissues and the
image is diplayed on the screen in the form of scans.
The crust and the upper mantle cracks and
forms the tectonic plate. The Tectonic
Plates causes Earthquake.
| P-Wave | S-Wave |
· They are longitudinal · They are faster than · They can travel through · They can pass through | · They are transverse · They are slower than other waves · They travel through · S-waves cannot pass |
P and S Wave travel through the Mantle
changing directions with depth.
P waves refract at the boundary between mantle and outer core.
S waves being transfer do not travel through liquid outer core.
1. Liquid Outer core under the Mentle.
Shadow zones are detected as P waves refract twice.
Once while entering the core from the mantle
and leaving the core from the mantle. Since
the refraction is further away forming shadow
zones it suggests a liquid outer core under the mantle.
2. Solid Inner Core
Weak P waves in the shadow zones caused by the
refraction of P waves while crossing the boundary
between outer core and inner core.
Long (L-waves) travel the slowest.
They happen only in the Earth’s
crust and they cause more violent
movements.
Gamma rays are produced when
the radiactive substance emit
nuclear radiations.
1. They are uses to disinfect food
and surgical equipment.
2. It is used to kill cancer cells. In
gamma treatment, the cobalt 60 is
used to direct the gamma radiation to
the cancer cells and kill it without
affecting the surrounding tissue.
1. Gamma Rays are highly ionizing.
2. Exposure to low dose of Gamma Rays can cause
gene mutation, DNA damage and even cancer.
3. Exposure to high dose of Gamma radiation
can caused killing of the cell.
They are produced by stopping
high speed electrons.
PROPERTIES
1. They are electromagnetic wave which travels
with the speed of light.
2. They have wavelength greater
than Gamma Rays but smaller than
ultraviolet rays.
3. They have lower frequency than
Gamma Rays but greater than
ultraviolet rays.
4. Their wavelength is about the diameter
of the atom.
1. Shorter wavelength X-rays are
used in X-ray therapy
to kill cancer cells without
destroying the healthy cells.
2. Longer wavelength X-rays are used
to photograph the internal structure
of the body.
1. X-Rays are highly ionizing
2. Exposure to a low dose of Gamma Rays can cause
gene mutation, DNA damage and even cancer.
3. Exposure to a high dose of Gamma radiation
can caused killing of the cell.
1. They are produced from the Sun.
The Sun is the source of ultraviolet
rays.
1. They are electromagnetic wave which travels
with the speed of light.
2. They have wavelength greater
than X-Rays but smaller than
Violet light.
3. They have lower frequency than
X- Rays but greater than
violet light.
They are uses as fluorescent markers
or fluorescent lamps which contains the
chemical which converts UV Light
to Visible Light.
1. They can cause sunburn and suntan
2. They can also lead to skin cancer.
3. They can also lead to blindness.
1. Sun and lamps emits light
2. It is the only part of the
specturm which is visible.
1. It is made up of 7 colours
2. VIOLET
INDIGO
BLUE
GREEN
YELLOW
ORANGE
RED
3. When the white light is passed
through the prism, it can give the
spectrum of colours.
Too much exposure to visible light
can lead to cancer, blindness and
skin damage.
1. They are electromagnetic wave which
travels
with the speed of light.
2. They have wavelength greater
than visible light but smaller than
Microwaves.
3. They have a lower frequency than visible
light but greater than
microwaves.
1. They are used in optical fibres
for communication.
2. They are used in remote
controls.
3. They are used as infrared
scanners to detect heat produced
by the body and unhealthy
tissues
4. Infrared cameras helps
to see objects in dark.
1. They can cause sunburn and suntan
2. They can also lead to skin cancer.
3. They can also lead to blindness.
The water in the food
absorb microwaves and
become heated and heats the
food preventing the microwave
from heating as it has no water.
1. They are electromagnetic wave which
travels
with the speed of light.
2. They have wavelength greater
than infrared light but smaller than
Radiowaves.
3. They have a lower frequency than
infrared light but greater than
radiowaves.
4. They are found between Radiowaves
and Infrared Waves.
1. They are used in communication.
2.They are used in satellite TV.
3. They are used in cooking.
4. They are used to carry mobile phone
signal.
1. Exposure to microwaves can heat
the body tissues.
2. Exposure to high dose of
microwaves can cause eye damage
and even cataract.
Radio waves can be generated by natural sources
such as lightning or astronomical phenomena; or
by artificial sources such as broadcast radio
towers, cell phones, satellites and radar.
1. They are electromagnetic wave which
travels
with the speed of light.
2. They have the highest wavelength.
3. They have the lowest frequency.
1. Exposure to radiowave can heat
the body tissues.
2. Exposure to high dose of
radiowaves can cause eye damage
and even cataract.
They are used to refract the light and forms the image of an
objects. They are used in camera.
| CONVEX LENS | CONCAVE LENS |
1. It is a converging lens 2. It is thicker at the center 3. It has a real focus 4. It converges a parallel 5. It is used in microscope, 6. Used to correct short sight | 1. It is a diverging lens. 2. It is thinner at the center 3. It has a virtual focus 4. It diverges a parallel beam 5. Used in some telescopes 6. Used to correct long sight. |
mages formed is virtual, upright
and smaller than the object.
2. Reflection on a smooth surface.
3. Reflection on a rough surface.
I have tried my level best to cover the maximum of your specification. But this is not the alternative to the textbook. You should cover the specification or the textbook thoroughly. This is the quick revision to help you cover the gist of everything. In case you spot any errors then do let us know and we will rectify it.
References:
BBC Bitesize
Wikipedia
Wikimedia Commons
Image Source:
Wikipedia
Wikimedia
Commons
Flickr
Pixabay
Make sure you have watched the above videos and are familiar with the key definations before trying these questions. It is also good to time yourself while doing these questions so that you can work on the speed as well.