Table of Contents
Week 1 | English Grammar
Week 2 | English Grammar
Week 3 | English Grammar
Week 4| English Grammar
Week 5| English Grammar
Week 6| English Grammar
Week 7| English Grammar
Week 8| English Grammar
Week 9| English Grammar
Week 10| English Grammar
Week 11| English Grammar
Week 12| English Grammar
Week 13| English Grammar
Electromagnetic waves – EM Waves
Now this is what our knowledge on waves largely focus on. You might be thinking waves are useless why do I want to know about them.
But let me tell you what Em waves are used for and in:
Radio waves – television, radio and communication technology. Even used in phones, planes and astronomy.
These can travel long distances and penetrate materials well without being costly to make.
Microwaves – Cooking food, satellites and GPS.
They interact with water molecules so there perfect for heating our food.
There’s little microwave radiation arriving from outside our planet, so it doesn’t experience much interference.
Infrared (IR) – Heaters, cooking food, cameras, thermal imaging, mobile phones, Wi-Fi and Bluetooth. Phone signals, mobile data and
Bluetooth all work because of IR waves.
IR is great it travels far and isn’t absorbed by much even our atmosphere won’t absorb it. Its also easily generated so it’s a very practical source.
Visible light – Your sight, fibre optics and anything you can see.
Experiences high interference so its only used when we can make sure there’s little outside interference.
This is why fibre optics are two glass layers sealed in plastic. This prevents noise pollution and has total internal reflection leading signals to the ends of the cable.
Ultraviolet (UV) – Efficient lamps, sun tanning, Wi-Fi, invisible ink, black lights and cleaning medical equipment.
Reacts with our bodies and gives us vitamin D. It can also generate extreme conditions that can kill bacteria.
X-rays and Gamma – Medical imaging; x-rays, MRI machines. Most of the cancer treatment currently being researched involves lasers using these Em waves to kill cancer cells.
Great at penetrating objects as a result it lets us see into our bodies and due to its extremely energetic nature it can kill cancer and bacteria.
Em waves are special waves they don’t need a medium to travel through and are the main method of energy transfer.
Em waves also have the same speed in the same mediums
regardless of frequency or wavelength.
Em waves have a speed of 3 x 108ms-1. Light and radiation are Em waves.
Em waves have a wide spectrum of wavelengths.
Human beings can’t see any Em waves outside of the visible range.
The rest of the Em spectrum is grouped by the frequency of the waves.
The higher frequency waves carry more energy.
Em waves transfer energy in multiple ways. The simplest way to look at them is how direct sun light can heat and melt ice.
Another example is using solar rays to generate electrical energy using solar panels.
There is also the fact that exited atoms will emit Em waves to lose energy and become more stable.
Em waves can interact with matter in very complicated ways as well.
Some substances will absorb light and emit multiple waves at lower frequencies to release all the energy. This is due to the complicated structure of the molecules in substances.
Molecules will also absorb reflect and transmit Em waves differently.
For example, the bullet shrimp appear to be plain and look alike to our eyes but when looked at under an ultra violet lamps they have beautiful patterns, a similar effect is also observed with butterflies.
This happens as these creatures can see light outside our range of vision.
Em waves get diffracted as their
speed changes from medium to medium, just remember nothing can go faster than 3 x 108 ms--1.
Em waves can be generated in many ways. Almost everything can make Em waves as a bi product.
However, radio waves are mostly made by our electrical systems and
thermal radiation. When charged particles oscillate/vibrate in electrical systems they generate radio waves.
In electrical systems ac currents generate radio waves.
Then when radio waves are absorbed into electrical systems they will make an ac current just like the one that made it.
Combining this knowledge with what we know about crystals we built telephones and radios.
When electrons are exited and de-exited or reactions occur Em waves can be generated or absorbed from across the spectrum, but Gamma rays only occur when changes happen in the nucleus of an atom.
This happens as a massive amount of energy is required to create a photon at those frequencies.
This is why radiation is so harmful to us. Since gamma rays and x- rays are made in the nucleus when absorbed they can change the atoms that make up our DNA, changing our cells and damaging our bodies. This is how cancer forms.
UV can damage skin, permanently aging it as well as the potential of skin cancer.
Low levels of radiation are negligible, they can affect us but the chance of any damage happening is too low for it to matter.
All the colours we see are narrow bands of light in the visible spectrum. This can help us understand absorption and emission.
Looking at colour filters we see that they absorb all the light besides the colour we see them at.
This is because the rays they don’t absorb are the ones that are transmitted and reach our eyes.
Objects will also transmit differently this leads to translucent and transparent objects.
Transparent objects will transmit all light as they are see through. Translucent objects will show non-absorbed light as white and the rest as black.