EM Waves Flashcards
What are the 7 types of waves
Radio Micro Infra red Visible light Ultra violet X-ray Gamma ray
What is the longest wavelength
Radio waves
What is the shortest wavelength
Gamma rays
What is the same about all the EM waves travelling in a vacuum
They travel in the same direction
EM waves with higher frequencies have…
Shorter wavelengths
Why do EM waves have different purposes
They have different properties
What is the main use of radio waves
Communication
What is the general size of radio waves
Longer than 10cm
Why is it possible for long-wave radio to be transmitted from London to hallway around the world
Long wavelengths diffract around the curved surfaces of the earth
What does the diffraction effect enable
Radio signals to be received regardless of whether the receiver is in line with the transmitter
Why can short wave radio signals be received at long distances
They reflect of the ionosphere
What is the ionosphere
An electrically charged layer in the earth’s upper atmosphere
Where are medium-wave signals reflected from
The ionosphere
What does reflection of medium-wave signals depend on
The atmospheric conditions and the time of day
What are microwaves used for
Satellite communication
Mobile phones
Why are microwaves used for satellite communication instead of radio waves
They can pass through the earth’s watery layer whereas microwaves can’t
Where do mobile phone micro-waves travel between
Phone and the transmitter
Why do some people think living near a mast or excessive use of your mobile phone is dangerous
Some wavelengths of microwaves are absorbed by water molecules and heat them up. If this water happens to be if your cells you might start to cook
Is their any conclusive evidence for why people think using a mobile phone may be damaging to your health
No
how do remote-sensing satellites use microwaves
To see through the clouds
Monitor oil spills
Track iceberg movement
See how much of a rainforest has been deforested
What are infrared waves used for
Remote controls
Optical fibers
What is the main remote control that uses infrared waves
Wireless remote controls
How do remote controls work
Emit different patters of infrared waves to send different commands to the appliance
What do optical fibers do
Carry data over long distances quickly
What other waves - apart from infra red - do optical fibers and remote controls use
Visible light
how do infrared waves work
The signal is carried as pulses or infra red radiation and is reflected off the sides of a very narrow core from one end of the fiber to the other
What is visible light useful for
Photography
What do cameras use to focus on visible light
The lens
Where do cameras focus visible light onto using a lens
A light - sensitive film or electronic sensor
What does the lens aperture do
Controls how much light enters the camera
What does the shutter speed of a camera determine
How long the film or sensor is exposed to light
What can a photographer do by varying the lens aperture and shutter speed of a camera
Capture as much or as little light as they want in their photograph
