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P6 H) Electromagnetic Spectrum – Part 3
P6 H) Electromagnetic Spectrum – Part 3
Microwaves
Microwaves are used by both satellites for communication and to heat up food (in a microwave oven). We will look at these seperately
Satellites
Microwaves are used in communication to and from satellites. Microwaves are used because the microwaves are able to pass through the earth’s watery atmosphere (the clouds and water vapour in the atmosphere). Satellite TV works by a transmitter on earth transmitting microwaves into space where the microwaves are received by a receiver dish on a satellite. The satellite then transmits the signal back down to earth in a different direction where it is received by a satellite dish on the ground (such as a dish on the side of your house). There is a short delay between the signal being sent from the transmitter on earth and being received by the satellite dish on the side of your house; this delay is due to the large distances that the microwaves have to travel.
Microwaves are used by both satellites for communication and to heat up food (in a microwave oven). We will look at these seperately
Satellites
Microwaves are used in communication to and from satellites. Microwaves are used because the microwaves are able to pass through the earth’s watery atmosphere (the clouds and water vapour in the atmosphere). Satellite TV works by a transmitter on earth transmitting microwaves into space where the microwaves are received by a receiver dish on a satellite. The satellite then transmits the signal back down to earth in a different direction where it is received by a satellite dish on the ground (such as a dish on the side of your house). There is a short delay between the signal being sent from the transmitter on earth and being received by the satellite dish on the side of your house; this delay is due to the large distances that the microwaves have to travel.
Microwave Ovens
The microwaves used for communication in satellites are able to the pass through the water molecules in the atmosphere (the clouds and water vapour).
The microwaves used in microwave ovens have higher frequencies and shorter wave lengths. This means that the microwaves from a microwave oven are absorbed by the water molecules in the food. When the microwaves are absorbed by the water molecules in the food, the microwaves transfer energy to the thermal energy stores of the water molecules, thus causing the water molecules to heat up. The water molecules then transfer some of this thermal energy to the rest of the molecules in the food, which cooks the food; the water molecules transfer this energy by heating. The microwaves from the microwave oven are able to penetrate a short distance into the food before they are absorbed by the water molecules.
The microwaves used for communication in satellites are able to the pass through the water molecules in the atmosphere (the clouds and water vapour).
The microwaves used in microwave ovens have higher frequencies and shorter wave lengths. This means that the microwaves from a microwave oven are absorbed by the water molecules in the food. When the microwaves are absorbed by the water molecules in the food, the microwaves transfer energy to the thermal energy stores of the water molecules, thus causing the water molecules to heat up. The water molecules then transfer some of this thermal energy to the rest of the molecules in the food, which cooks the food; the water molecules transfer this energy by heating. The microwaves from the microwave oven are able to penetrate a short distance into the food before they are absorbed by the water molecules.
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Infrared Rays
All objects emit infrared radiation. The hotter an object is, the more infrared radiation it will emit. Humans are unable to see infrared radiation, but we can use infrared cameras to monitor infrared radiation emitted by objects. Infrared cameras work by detecting the amount of infrared radiation giving out by objects and converting it into an electrical signal. This electrical signal can then be viewed on a screen or as a picture. The hotter an object is, the more infrared radiation it will emit and the brighter the object will appear on the image produced by the infrared camera. Infrared cameras are used to film wildlife at night and the military use infrared cameras to carry out operations at night.
All objects emit infrared radiation. The hotter an object is, the more infrared radiation it will emit. Humans are unable to see infrared radiation, but we can use infrared cameras to monitor infrared radiation emitted by objects. Infrared cameras work by detecting the amount of infrared radiation giving out by objects and converting it into an electrical signal. This electrical signal can then be viewed on a screen or as a picture. The hotter an object is, the more infrared radiation it will emit and the brighter the object will appear on the image produced by the infrared camera. Infrared cameras are used to film wildlife at night and the military use infrared cameras to carry out operations at night.
Infrared radiation can be absorbed by some chemical bonds. When the infrared radiation is absorbed, energy is transferred to the energy of the bonds, which causes heating; the thermal energy stores of the object increases – the object gets hotter. We use infrared radiation to heat rooms using an electric heater and when we cook food. An electric heater has a long wire that heats up when a current passes through it. When the wire is hots, it emits large quantities of infrared radiation. This infrared radiation can be absorbed by the air and objects in the room, which transfers energy to the thermal energy stores of the objects, resulting in the temperature of the room increasing.
Visible Light
Visible light is the only part of the electromagnetic spectrum that humans can see. Visible light is used in fibre optic cables. We use fibre optic cables to transport data across long distances; fibre optic cables are used in our internet and phone systems.
Fibre optic cables work because the visible light is always reflected within the glass fibre even when the fibre optic cable is bent; this is sometimes referred to as total internal reflection. There is a diagram of this taking place below.
Visible light is the only part of the electromagnetic spectrum that humans can see. Visible light is used in fibre optic cables. We use fibre optic cables to transport data across long distances; fibre optic cables are used in our internet and phone systems.
Fibre optic cables work because the visible light is always reflected within the glass fibre even when the fibre optic cable is bent; this is sometimes referred to as total internal reflection. There is a diagram of this taking place below.
At the transmitting source (such as a data centre), the light is encoded with some data. The light with the data then travels down the fibre optic to a receiving end where the data is then decoded (such as a computer).
A fibre optic cable has a glass fibre in the centre where the light that is encoded with data travels down. The glass fibre has some glass cladding that protects the fibre and ensures that the light stays inside the glass fibre centre.
We use light to transmit the data because it is easy to refract so that it remains in the fibre optic. Also, the light does not easily scatter or get absorbed.
A fibre optic cable has a glass fibre in the centre where the light that is encoded with data travels down. The glass fibre has some glass cladding that protects the fibre and ensures that the light stays inside the glass fibre centre.
We use light to transmit the data because it is easy to refract so that it remains in the fibre optic. Also, the light does not easily scatter or get absorbed.
Ultraviolet
Ultraviolet light from the sun is what gives you a suntan. Excessive ultraviolet radiation can be dangerous as it can cause skin cancer, sunburn, premature aging of the skin (wrinkles, leathery skin etc) and even eye problems. Individuals may also try to get a suntan by going on tanning beds that have lights that give out UV radiation. Overexposure to UV radiation on these tanning beds can cause the same effects on the body (skin cancer, sunburn etc).
Some chemicals are fluorescent, which means that they absorb ultraviolet radiation and reemit it as visible light. This is why certain parts of our clothing, teeth and paints look very bright under ultraviolet light.
Ultraviolet light from the sun is what gives you a suntan. Excessive ultraviolet radiation can be dangerous as it can cause skin cancer, sunburn, premature aging of the skin (wrinkles, leathery skin etc) and even eye problems. Individuals may also try to get a suntan by going on tanning beds that have lights that give out UV radiation. Overexposure to UV radiation on these tanning beds can cause the same effects on the body (skin cancer, sunburn etc).
Some chemicals are fluorescent, which means that they absorb ultraviolet radiation and reemit it as visible light. This is why certain parts of our clothing, teeth and paints look very bright under ultraviolet light.
Fluorescent lights have phosphor on the inside of the bulb. The phosphor has fluorescent characteristics. The fluorescent lights give out ultraviolet radiation, which is absorbed by the phosphor inside the bulb and reemitted as visible light making the lights extremely bright. Fluorescent lights are very energy efficient; they don’t cost much money to run.
We can use security pens to identify property. For example, you may use a security pen to write your postcode or phone number on your bike. The writing from the security pen will not be visible under visible light, but will be visible under ultraviolet light as the fluorescent ink will absorb the UV waves and then remit it as visible light. So, if you lost your bike, the police could identify whether a bike being sold on the internet is or is not your bike by shinning a UV light where you have written your post code or phone number (it is definitely worth writing your phone number or post code on your bike).
We can use security pens to identify property. For example, you may use a security pen to write your postcode or phone number on your bike. The writing from the security pen will not be visible under visible light, but will be visible under ultraviolet light as the fluorescent ink will absorb the UV waves and then remit it as visible light. So, if you lost your bike, the police could identify whether a bike being sold on the internet is or is not your bike by shinning a UV light where you have written your post code or phone number (it is definitely worth writing your phone number or post code on your bike).
X-Rays and Gamma Rays
X-rays are used in medical equipment to see internal structures of body parts. For an X-ray machine, X-rays are fired at an individual’s body part, such as an arm. The X-rays are able to pass through flesh and are unable to pass through bones as they are denser. The X-rays that make it through the body mark a metal screen. This creates an image of the inside of the body like what is shown below.
X-rays are used in medical equipment to see internal structures of body parts. For an X-ray machine, X-rays are fired at an individual’s body part, such as an arm. The X-rays are able to pass through flesh and are unable to pass through bones as they are denser. The X-rays that make it through the body mark a metal screen. This creates an image of the inside of the body like what is shown below.
From the X-ray image, we can then see whether the bones look normal or if there are any breaks in the bones.
X-rays and gamma rays are used to treat individuals with cancer in a process that is known as radiotherapy. Cancer is where the cells in part of the body are multiplying uncontrollably and it results in a growth or a tumour. Individuals undergoing radiotherapy have beams of X-rays and gamma rays fired at the tumour. The X-rays and gamma rays kill the tumour cells which hopefully stops the tumour expanding. When we undertake radiotherapy, we need to reduce the number of normal cells (non-cancerous cells) that are exposed to the X-rays and gamma rays because we want to minimise the number of normal cells killed by the X-rays and gamma rays.
Gamma rays and X-rays are used to sterilise food and hospital equipment. This is because they kill any microorganisms that are living on the object that we are sterilising.
We are able to use substances known as medical tracers that emit gamma radiation to see if there are certain issues in the body. For example, we can use medical tracers to see if an individual has a tumour that may be cancerous or an internal bleed somewhere in the body. The medical tracers work by an individual swallowing a substance (this is usually a liquid). The medical tracer will pass into the bloodstream and move around the body. Medical professionals follow the medical tracers progress around the body by looking for the gamma rays that are produced; they can use what is known as a PET scanner. Areas that have an internal bleed or a tumour will have a high blood supply, which means that they will have a lot of the tracer and will therefore produce large quantities of gamma radiation. The PET scanner will be able to locate and estimate the size of a tumour or internal bleed.
X-rays and gamma rays are used to treat individuals with cancer in a process that is known as radiotherapy. Cancer is where the cells in part of the body are multiplying uncontrollably and it results in a growth or a tumour. Individuals undergoing radiotherapy have beams of X-rays and gamma rays fired at the tumour. The X-rays and gamma rays kill the tumour cells which hopefully stops the tumour expanding. When we undertake radiotherapy, we need to reduce the number of normal cells (non-cancerous cells) that are exposed to the X-rays and gamma rays because we want to minimise the number of normal cells killed by the X-rays and gamma rays.
Gamma rays and X-rays are used to sterilise food and hospital equipment. This is because they kill any microorganisms that are living on the object that we are sterilising.
We are able to use substances known as medical tracers that emit gamma radiation to see if there are certain issues in the body. For example, we can use medical tracers to see if an individual has a tumour that may be cancerous or an internal bleed somewhere in the body. The medical tracers work by an individual swallowing a substance (this is usually a liquid). The medical tracer will pass into the bloodstream and move around the body. Medical professionals follow the medical tracers progress around the body by looking for the gamma rays that are produced; they can use what is known as a PET scanner. Areas that have an internal bleed or a tumour will have a high blood supply, which means that they will have a lot of the tracer and will therefore produce large quantities of gamma radiation. The PET scanner will be able to locate and estimate the size of a tumour or internal bleed.
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Summary of Uses
Here is a summary of the different groups in the EM spectrum and their uses starting from the longest wavelength and lowest frequency (radio waves) to the shortest wavelength and highest frequency (gamma).
Here is a summary of the different groups in the EM spectrum and their uses starting from the longest wavelength and lowest frequency (radio waves) to the shortest wavelength and highest frequency (gamma).
- Radio waves – communication, television and radio
- Microwaves – satellite communications, cooking food
- Infrared – electrical heaters, cooking food, infrared cameras
- Visible light – fibre optic communications
- Ultraviolet – energy efficient lamps, sun tanning
- X-rays and gamma rays – medical imaging and treatments.