Electromagnetic waves Flashcards
electromagnetic spectrum in order
- Radio waves
- Micro waves
- Infra red
- Visible light
- Ultra violet
- X-rays
- Gamma rays
Transverse waves
The oscillations are perpendicular to the direction of energy transfer
What are EM waves?
Transverse waves that tranfer energy from a source to an absorber
How do EM waves travel through air or a vacuum?
At the same speed
EM waves wavelengh and frequency are ______ ______?
Inversely related
Electromagnetic spectrum as you go left to right
Frequency increases
wavelength decreases
Where does EM waves come from?
Everywhere
When an EM wave come into contact with something what happens?
- Reflected
- Absorbed
- Transmitted
Radio waves properties
-Lowest frequency
-Longest wavelength (+10cm)
Why are EM waves called EM
Generated of oscillations (alternating current) of electric and magnetic fields
What do we use to generate radio waves
Transmitter Which is usually connected to an oscilloscope
Oscilloscope
See the frequency of the alternating current
- determines the frequency of the wave
In radio waves, what is the absorber?
The receiver which generates an A.C. and is displayed on another oscilloscope
The oscilloscope of the reveiver and the oscilloscope of the transmitter have ____ _____ ______ frequency
The exact same
Radio waves uses
Allows us to transfer information (communication)
3 Radio waves for communication
- Long waves
- Short waves
- Very short waves
Why are long waves used for huge distances?
The waves diffract (bend) around the curved surface of the earth
- wavelength=1-10km
How do shortwaves travel long distances?
They are unable to diffract around the earth so they reflect from the ionosphere
- wavelegnth=10m-100m
ionosphere
An electrically charged layer in the Earth’s upper atmosphere
Very short waves
- TV
- FM radio
Direct travel
Infrared and microwaves properties
-Low frequency
-long wavelengths
Microwaves that aren’t absorbed by water molecules, uses
Used for communication using satellites as they can pass easily through the earth’s watery atmosphere
How do satellites use microwaves
- The signal from a transmitter is transmitted
into space - Satellite receiver dish picks up the signal
- The satellite transmit the signal back to earth
in a different direction - A satellite dish on the ground receives the
signal - slight time delay between the signals being
sent and received because of the long
distances.
Microwaves that are absorbed by water molecules, uses
Used in microwaves and ovens to heat our food
How do ovens use microwaves
Since a lot of our food contain water molecules is absorbs the microwaves waves.
- This gives the water molecules energy making
them vibrate more, transferring some energy
to the neighboring molecules so it spread
throughout the food
Infrared radiation
Emitted from all objects that have thermal energy
- The hotter the object the more IR radiation it
gives out
Infrared cameras
Detects IR radiation and turns it into electrical signals, which are them displayed onto the screen as a picture
- The hotter the object the brighter it is
IR radiation for cooking
Heating metal to very high temp, it can emit lots of IR radiation which can then heat our food by transferring the heat energy.
-Doesn’t penetrate the surface
Visible light
What are colours are the longest and shortest wave lengths
- Red is the longest
- Violet is the shortest
What can visible light be used for?
Communication through optic fibres
What are the advantages of optical fibres?
- Transmit much more info
- Signals is less likely to be distorted
Fluorescence
It is a property of certain chemicals where UV radiation is absorbed and then emit visible light
Fluorescent lights
- generates UV radiation
- This radiation is then absorbed by a layer of
phosphorus - Phosphorus has so much energy so it re-
emits the energy as visible light
Benefits of fluorescent lights
energy efficient
- save energy bills
- save carbon dioxide emissions
X-rays and Gamma rays properties
-Short wavelengths
-high frequency
How are X-rays used to see the internal view of objects
- fire x-rays at a person’s body and record the
waves that get through using a detector plate - This works by denser materials, like bones,
absorb the waves - EM waves easily passes through our flesh
What are the 2 uses of gamma rays for sterilization
- Food
- Medical equipment
Gamma rays
Can kill microorganisms without causing any damage
X-rays and Gamma rays in medicine
- Ionising radiation that can kill our cells leading
to cancer - Help us to treat/diagnose diseases
