Microwaves: internal heating of body tissue
Problem: Microwaves have a similar frequency to the vibrations of many molecules and so they can increase these vibrations, resulting in internal heating. In this way, microwaves can internally heat human body tissue.
Protective measure: microwaves ovens need to have shielding to prevent microwaves escaping and reaching the person using it (or anyone else around)
Infrared: skin burns
Problem: he infrared range of frequencies can make the surface molecules of substances vibrate, like microwaves, this results in a heating effect. However, infrared has a higher frequency, so it carries more energy than microwave radiation. IF human flesh is exposed to too much IR radiation, skin burns can result.
Protective measure: you can protect yourself using insulating materials to reduce the amount of IR reaching your skin.
Ultraviolet: damage to surface cells and blindness
Problem: UV radiation can damage surface cells and cause blindness. It is 'ionising', this means it carries enough energy to knock electrons off atoms. This can case cell mutations (which can lead to cancer)
Protective measure: Wear suncream with UV filters if out in the sun and stay out of strong sunlight
Gamma rays: cancer, mutation
Problem: Gamma rays have very high frequency and are ionising, they carry more energy than UV rays and therefore can penetrate the body much further. They can cause cell mutation or destruction, which leads to tissue damage and cancer.
Protective measure: Radioactive sources of gamma rays should be kept in lad-lined boxes when not in use. Should someone need to be exposed to gamma radiation(e.g. in chemotherapy) the exposure time should be kept as short as possible.
Source of most information: CGP
Showing posts with label the electromagnetic spectrum. Show all posts
Showing posts with label the electromagnetic spectrum. Show all posts
Wednesday, 23 March 2016
3.12 explain some of the uses of electromagnetic radiations
Radio waves: broadcasting and communications
Radio waves are used mainly for communication. This is because they have long wavelengths (over 10m) which s very useful. Long-wave radio (wavelengths of 1-10km) can be transmitted from London (for example) to half way around the globe. This is because long wavelengths are the best at diffracting, so they can bend around the earth and also arounds opticals such as hills and tunnels.
Radio waves used for broadcasting have mush shorter wavelengths (10cm-10m), these do not bend well so you have to be in direct sight of the transmitter, the is why T.V ariels are positioned on top of houses.
NOTE: as well as long-wave radio signals, short-wave and medium-wave also exist. Short wave radio signals (10m-100m) can also be received long distance from the transmitter because they are reflected from the ionosphere (an electrically charged layer in the Earth's upper atmosphere). Medium-wave signals can also reflect from the ionosphere (but this depends on the atmospheric conditions and the time of day)
Microwaves; cooking and satellite transmissions
Microwaves have wavelengths of around 1cm-10cm, they are used for satellite communication and cooking.
Satellite communication needs to use wavelengths of microwaves which can easily pass through the Earths atmosphere without bing absorbed. For a satellite T.V (for example) to work, the signal from a transmitter is transmitted into space where it is picked up by the satellite receiver did that is orbiting thousands of kilometre above Earth. The satellite transmits the signal back to Earth in a different direction where it is received by a satellite dish on the ground. Mobile phone calls also travel as microwaves from your phone to the nearest transmitter.
Microwaves in ovens have a different wavelength to those used in communication. These microwaves penetrate a few centimetres into the food before being absorbed by water molecules in the food.
Infrared: heaters and night vision equipment
Infrared radiation is also known as heat radiation. Infrared radiation is given out anything and everything, and the hotter the object, the more IR radiation is given out. Examples of infrared radiation in everyday phenomena include electrical heaters and grills. Electrical heaters radiate infrared to keep us warm and grills radio infrared to cook food.
Furthermore, the infrared radiation that objects give out can be picked up/detected during nighttime (or pitch black) by night-vision equipment. the equipment turns the IR that has been radiated into an electrical signal which is displayed on a screen as a picture, meaning things that otherwise would go amiss (e.g. a criminal hiding) to be seen.
Visible light: optical fibres and photography
Visible light can also be used in communication using optical fibres which carry data over long distances as pulses of light.
Optical fibres work by bouncing waves off the sides of a very narrow core. The beam of light enters the fibre at a certain angle as one end and is reflected again and again (known as 'total internal reflection' until it emerges at the other end...
Optical fibres are often used for telephone and broadband internet cables. They are also used in hospitals to see inside the body without having to operate.
Visible light is also used for photography. Cameras use a lens to focus visible light onto a light-sensitive film or electronic sensor (the lens aperture controls how much light enters the camera). The shutter speed determine how long the film or sensor is exposed to the light. by varying the aperture and shutter speed a photographer can capture as much/little light as they want
Ultraviolet: fluorescent lamps
Florescent colours look so bright because it is where ultraviolet radiation (UV) is absorbed and visible light is emitted.
This basically means that fluorescent lights use UV radiation to emit visible light. They are safe to use as nearly all the UV radiation is absorbed by a phosphor coating on the inside of the glass (which emits visible light instead). This is more energy-efficient than filament light bulbs.
X-rays: observing the internal structure of objects and materials and medical applications
To produce an X-ray image, X-ray radiation is directed through your body (or an object you wish to X-ray) onto a detector plate (which starts off white). X-rays can easily pass through mediums such as flesh but not through dense mediums such as bone. The brighter bits (e.g. bones) are where fewer X-rays get through - this is a negative image.
Gamma rays: sterilising food and medical equipment
Medical equipment is sterilised by gamma rays as they kill ass the microbes. This is more effective than boiling equipment as this could potentially cause damage.
Food can be sterilised the same was as medical equipment (by killing the microbes). Is is perfectly safe to eat afterwards, as in like its not radioactive etc.
Radio waves are used mainly for communication. This is because they have long wavelengths (over 10m) which s very useful. Long-wave radio (wavelengths of 1-10km) can be transmitted from London (for example) to half way around the globe. This is because long wavelengths are the best at diffracting, so they can bend around the earth and also arounds opticals such as hills and tunnels.
Radio waves used for broadcasting have mush shorter wavelengths (10cm-10m), these do not bend well so you have to be in direct sight of the transmitter, the is why T.V ariels are positioned on top of houses.
NOTE: as well as long-wave radio signals, short-wave and medium-wave also exist. Short wave radio signals (10m-100m) can also be received long distance from the transmitter because they are reflected from the ionosphere (an electrically charged layer in the Earth's upper atmosphere). Medium-wave signals can also reflect from the ionosphere (but this depends on the atmospheric conditions and the time of day)
Microwaves; cooking and satellite transmissions
Microwaves have wavelengths of around 1cm-10cm, they are used for satellite communication and cooking.
Satellite communication needs to use wavelengths of microwaves which can easily pass through the Earths atmosphere without bing absorbed. For a satellite T.V (for example) to work, the signal from a transmitter is transmitted into space where it is picked up by the satellite receiver did that is orbiting thousands of kilometre above Earth. The satellite transmits the signal back to Earth in a different direction where it is received by a satellite dish on the ground. Mobile phone calls also travel as microwaves from your phone to the nearest transmitter.
Microwaves in ovens have a different wavelength to those used in communication. These microwaves penetrate a few centimetres into the food before being absorbed by water molecules in the food.
Infrared: heaters and night vision equipment
Infrared radiation is also known as heat radiation. Infrared radiation is given out anything and everything, and the hotter the object, the more IR radiation is given out. Examples of infrared radiation in everyday phenomena include electrical heaters and grills. Electrical heaters radiate infrared to keep us warm and grills radio infrared to cook food.
Furthermore, the infrared radiation that objects give out can be picked up/detected during nighttime (or pitch black) by night-vision equipment. the equipment turns the IR that has been radiated into an electrical signal which is displayed on a screen as a picture, meaning things that otherwise would go amiss (e.g. a criminal hiding) to be seen.
Visible light: optical fibres and photography
Visible light can also be used in communication using optical fibres which carry data over long distances as pulses of light.
Optical fibres work by bouncing waves off the sides of a very narrow core. The beam of light enters the fibre at a certain angle as one end and is reflected again and again (known as 'total internal reflection' until it emerges at the other end...
Optical fibres are often used for telephone and broadband internet cables. They are also used in hospitals to see inside the body without having to operate.
Visible light is also used for photography. Cameras use a lens to focus visible light onto a light-sensitive film or electronic sensor (the lens aperture controls how much light enters the camera). The shutter speed determine how long the film or sensor is exposed to the light. by varying the aperture and shutter speed a photographer can capture as much/little light as they want
Ultraviolet: fluorescent lamps
Florescent colours look so bright because it is where ultraviolet radiation (UV) is absorbed and visible light is emitted.
This basically means that fluorescent lights use UV radiation to emit visible light. They are safe to use as nearly all the UV radiation is absorbed by a phosphor coating on the inside of the glass (which emits visible light instead). This is more energy-efficient than filament light bulbs.
X-rays: observing the internal structure of objects and materials and medical applications
To produce an X-ray image, X-ray radiation is directed through your body (or an object you wish to X-ray) onto a detector plate (which starts off white). X-rays can easily pass through mediums such as flesh but not through dense mediums such as bone. The brighter bits (e.g. bones) are where fewer X-rays get through - this is a negative image.
Gamma rays: sterilising food and medical equipment
Medical equipment is sterilised by gamma rays as they kill ass the microbes. This is more effective than boiling equipment as this could potentially cause damage.
Food can be sterilised the same was as medical equipment (by killing the microbes). Is is perfectly safe to eat afterwards, as in like its not radioactive etc.
3.11 identify the order of the electromagnetic spectrum in terms of decreasing wavelength and increasing frequency, including the colours of the visible spectrum
The electromagnetic spectrum is grouped into seven types of waves that have different wavelengths. The order is...
Radio waves (longest wavelength)
Microwaves
Infrared waves
Visible Light
Ultraviolet
X-Rays
Gamma rays (shortest wavelength)
NOTE: I use this song to remember the order... https://www.youtube.com/watch?v=ZPwG4zZNOu4
The colours of the visible light spectrum also depend on wavelength. The order is
Red (longest wavelength)
Orange
Yellow
Green
Blue
Indigo
Violet
NOTE: a good way to remember this is Richard Of York Gave Battle In Vain (sorry, may only work for english students as we learn this is history when were like 5 but if you can, try and remember it. Otherwise, if you have any other acronyms that are easy to remember, please comment them!)
Radio waves (longest wavelength)
Microwaves
Infrared waves
Visible Light
Ultraviolet
X-Rays
Gamma rays (shortest wavelength)
NOTE: I use this song to remember the order... https://www.youtube.com/watch?v=ZPwG4zZNOu4
The colours of the visible light spectrum also depend on wavelength. The order is
Red (longest wavelength)
Orange
Yellow
Green
Blue
Indigo
Violet
NOTE: a good way to remember this is Richard Of York Gave Battle In Vain (sorry, may only work for english students as we learn this is history when were like 5 but if you can, try and remember it. Otherwise, if you have any other acronyms that are easy to remember, please comment them!)
3.10 understand that light is part of a continuous electromagnetic spectrum which includes radio, microwave, infrared, visible, ultraviolet, x-ray and gamma ray radiations and that all these waves travel at the same speed in free space
The electromagnetic spectrum is a range of different frequency waves. The spectrum is split into radio, micro, infrared, light, ultra violet, x-ray and gamma. All of these waves travel at the same speed in a vacuum, they are also all transverse waves.
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