Radio and Microwaves Flashcards
Name the waves in the EM spectrum in descending wavelength
Radio Waves Microwaves Infrared Visible light Ultraviolet X-Rays Gamma Rays
What is the speed of light?
3 x 10^8 m/s
Describe the relationship between the wavelength and frequency of EM waves
They are inversely proportional
λ = v/f
What are the three types of Radiowaves?
Long, short and very short radiowaves
Describe and explain the uses of long radiowaves
- They can be transmitted large distances, (e.g. London to
Singapore) as they diffract around the curved surface of
the earth
Describe and explain the uses of short radiowaves
- They can be transmitted over relatively large distances as
they reflect off of the ionosphere. (they can’t diffract over
the earth’s surface like long waves) They can also be used to send data over short distances like Bluetooth.
Describe and explain the uses of very short radiowaves
- Used in TV and FM radio. They must also travel directly
from a transmitter to a receiver
Why would it be difficult to get a good radio signal in a travelling car?
Surrounding structures e.g. Hills and buildings would get in between the transmitter and receiver.
What is the ionosphere?
An electrically charged layer of the earth’s upper atmosphere
Describe how information can be transmitted through radio waves
- An ac current flows in the circuit the transmitter is connected to
- AC current is made up of oscillating electrons/charges
- As electrons oscillate in the transmitter, they produce radio waves
- (Producing alternating electric and magnetic fields
- Radio waves are transmitted and absorbed by receiver
- Energy carried by wave is transferred to electrons in material of
receiver - Causes electrons in receiver to oscillate
- Generating an alternating current with the same frequency as the original current used to generate the radio wave
The shorter the wavelength…
- The more information the wave can carry
- The less they spread out (so the signal doesn’t weaken)
- The lower their range
Describe and explain the uses of microwaves
- Microwaves that aren’t absorbed by water molecules are
used in TV broadcasting and satellite phone links, as they
can pass through the earth’s atmosphere - Microwaves that are absorbed by water molecules are
used in microwave ovens, by heating water molecules in
food, causing them to oscillate/vibrate and heat the food
via conduction
How are carrier waves used to carry information?
They alter the amplitude of a wave
What are people’s concerns about using radio/microwaves in phones?
mobile phone signals carried by microwaves which heat substances that absorb them. So if too much microwave radiation is absorbed, tissues in head (e.g. brain) may be damaged by heating effect.
What does the amplitude of an EM wave tell us?
The maximum field strength of the electrical and magnetic waves
(Energy carried by an EM wave is proportional to its amplitude squared)
