YOU ARE LEARNING:
Microwaves
Microwaves
Microwaves have the second to longest wavelength. They are used for satellite communications and radar, as well us to heat up the water content in food.
This shows the electromagnetic spectrum
Can you see where X-rays, visible spectrum, microwaves and radio waves are on the spectrum?
So X-rays have the shortest wavelengths, then comes the visible spectrum, then microwaves, and r****adio waves have the longest wavelengths.
Which statement correctly describes the properties of microwaves?
Out of these options, what do you think microwaves might be used for?
You can select multiple answers
Microwaves can sometimes be considered as very short, high energy radio waves. How do you think they can be generated?
Microwaves have the property that they can pass through the atmosphere and ionosphere. What do you think this useful for?
Like radio waves, microwaves are transmitted and received, so we can use them to transfer information.
This is used in satellite communication (for satellite and cable TV and mobile phones) and in speed cameras and radar, which bounce microwaves off moving vehicles.
Some people are concerned that microwaves transmitted and received by our mobile phones are harmful to us...
but mobiles only emit very low intensity microwaves and it is not certain that they are in fact harmful.
Depending on the wavelength, some microwaves can be absorbed by water and some cannot. Do you think microwaves used in satellite communications can be absorbed by water?
Microwaves, that can be absorbed by water, can heat materials by vibrating the water molecules in the material.
What is this property helpful for?
Microwave ovens heat up food by vibrating the water molecules in food and drinks.
The heat spreads through the food via conduction and convection. How much the material is heated up depends on how intense the radiation is and how long it is exposed to the radiation.
Microwaves are reflected by metal surfaces, but they can pass through glass and plastics. What material do you think the protective case in microwave ovens is made of?
The radiation is kept inside a microwave oven by the reflecting metal case and metal grid in the door. Why do you think it is important that the radiation cannot escape the oven?
To sum up!
Microwaves are electromagnetic waves with...
Microwaves are used for...
satellite communications and radar.
Microwaves are created by...
generating an AC which can be sent from a transmitter to a receiver. These microwaves cannot be not absorbed by water.
Microwaves which can be absorbed by water are used to heat up food.
These can be dangerous because we have water molecule in our cells which can absorb microwaves. If they do that, our tissue can burn.