The Electromagnetic Spectrum Flashcards
What are electromagnetic waves?
Electromagnetic waves are defined as:
Transverse waves that transfer energy from the source of the waves to an absorber.
What are the properties of the Electromagnetic spectrum?
All electromagnetic waves share the following properties:
- They are all transverse
-They all travel at 300, 000,000 m/s, the speed of light in a vacuum (free space).
- They can all be reflected and refracted
What is the speed of light?
3 X 10^8 metres per second
How many types of electromagentic waves are there and what do they form?
There are 7 types of electromagnetic waves, which all together form a continuous spectrum.
How is the electromagnetic spectrum arranged?
The electromagnetic spectrum is arranged in a specific order based on the wavelengths or frequencies from longest wavelength (lowest frequency) to shortest wavelength (highest frequency).
What does a long wavelength represent?
A long wavelength represents that the wave is low frequency and has a low energy.
What does a short wavelength represent?
A short wavelength represents that the wave has a high frequency and high energy.
What is the order of the electromagnetic spectrum? (from longest wavelength to shortest wavelength)?
Radio waves
Microwaves
Infrared
Visible light
Ultraviolet
X-Rays
Gamma rays
Which electromagnetic wave has the highest frequency?
The Gamma ray has the highest frequency.
Which electromagnetic wave has the lowest frequency?
The Radio wave has the lowest frequency.
How is radiation with higher energy harmful?
Radiation with higher energy is harmful as it highly ionising (meaning it has enough energy to remove an electron from an atom or molecule, causing it to become ionized. Ionizing radiation can cause chemical changes in cells and damage DNA.)
Harmful to cells and tissues, causing cancer (e.g. UV, X-rays, Gamma rays)
Explain radiation with a lower energy
Radiation with a low energy is useful for communications and less harmful to humans.
What is visible light (detailed)?
Visible light is defined as the range of wavelengths which are visible to humans and is the only part of the spectrum detectable by the human eye.
How much does light take up in the entire electromagnetic spectrum?
It only takes up 0 .0035% of the whole electromagnetic spectrum
Who can see beyond visible light? (give examples)
Many animals, such as birds, bees and certain fish , are able to
perceive beyond visible light and can see infra-red and UV wavelengths of light
What is something within the visible light spectrum that corresponds to a narrow band of wavelength
and frequency?
Each colour within the visible light spectrum corresponds to the narrow band of wavelength and frequency.
Which colour has the longest wavelength and what does this mean?
Red has the longest wavelength meaning it has the lowest frequency and energy.
Which colour has the shortest wavelength and what does this mean?
Violet has the shortest wavelength meaning it has the highest frequency and energy.
Explain how wavelength and frequency are connected.
Wavelnegth and frequency are inversely proportional meaning that an increase in wavelength is a decrease in frequency and a decrease in wavelength is an increase in frequency.
What does it mean if there is an increase in wavelength?
An increase in wavelength means there is a decrease in frequency
What does it mean if there is a decrease in wavelength?
A decrease in wavelength is an increase in frequency.
Use of radios
Communication (radio and TV)
Use of microwave
Heating food, satellite communication (WiFi, mobile phones, satellites)
Use of infrared
Infrared cameras, electrical heaters, heating or cooking things
Use of visible light
Seeing and taking photographs/videos and fibre optic communications.
Use of ulraviolet
Security marking (fluorescence), fluorescent bulbs (which are energy efficienct lamps) and for tannning beds (getting a suntan)
Use of X-rays
X-Ray images (medicine, airport security and industry)
Use of gamma rays
Sterilising medical instruments and treating cancer
What can microwaves be used for at very high intensities? (and why)
At very high intensities microwaves can aso be used to heat food, as the water molecules in the food absorb the energy of microwaves, this energy causes the temperature of the food to increase.
What is infrared emitted by and how can it be detected?
Infrared is emitted by warm objects and can be detected using special cameras (thermal imaging cameras).
Explain how security cameras can see in the dark
By infared, infrared is emitted by warm objcts and can be detected using special cameras and this can be used to allow them to see in the dark.
Explain how remote controls work
Remote controls have small infrared LEDs that can send invisble signals to an infrared receiver on a device such as a TV
Explain why fibre optic cables are used instead of visible light most of the times.
Infrared travels down fibre optic cables more efficiently than visible light.
Human eye can detect wavelengths from how many nanometres?
Human eye can detect wavelengths from 750 nanometres (red light) up to 380 nanometres (violet light)
Why and how do we get suntans?
We get suntans by ultraviolet, it’s our body’s way of protecting itself against the ultraviolet
What happens when certain substances are exposed to ultraviolet and what is this process known as?
They absorb and re-emit it as visibly light (making them glow) known as fluroescence.
What is fluorescence used for? (and give two examples)
It is used to secretly mark things using special ink, most bank note have invisible flurorescent markings on them and fluorescent light bulbs also use this principle to emit visible light.
Explain what happens to the denser parts of the body by X-rays
X-rays are absorbed by denser parts of the body, such as bones.
What happens when bones are exposed to x-rays?
When exposed to x-rays, the bones can cause a shadow which can be seen using a special x-ray detector or using photographic film.
How do gamma rays kill cancerous cells?
If gamma rays are carefully aimed at cancerous tissue, they can be very effective at killing it.
How do gamma rays sterilise things?
Gamma rays can be used to sterilise things by killing off the bacteria.
What happens beyond the visible part of the spectrum and what does this mean?
The energy becomes large enough to ionise atoms, meaning the danger associated with the EM waves increases along with the frequency.
How does the length of the wavelength affect how ionising the radiation is?
The shorter the wavelength , the more ionising the radiation and the longer the wavelength, the less ionising the radiation is.
Why are ultraviolet waves, X-rays and gamma rays hazardous?
Due to the fact they are highly ionising
What do the effect of dangerous electromagnetc waves depend on?
The effect depends on the type of radiation and size of the dose.
Highly ionsing electromagnetic waves can do what to cells?
They can damage cells and cause mutations, making them cancerous
Risk of radio waves
No known danger
Risk of micro waves
Possible heat damage to internal organs
Risk of infared waves
Skin burns
Risk of visible light waves
Bright light can cause eye damage
Risk of ultraviolet waves
Eye damage, sunburn and skin cancer
Risk of X-rays waves
Kills cells, causes mutations and cancer
Risk of gamma rays
Kills cells, causes mutations and cancer
Explain how microwaves can cause possible heat damage to human internal organs
Certain frequencies of microwaves are absorbed by water molecules and since humans contain a lot of water, there is a risk of internal heating from microwaves.
Why do some people believe microwaves are safe?
Due to the fact the energy is prevented from escaping the oven by metal walls and metal grid in the glass door.
How do sunglasses protect our eyes from ultraviolet waves?
Sunglasses absorb ultraviolet, preventing it from entering the eyes.
What is used to protect our eyes from ultraviolet waves and why?
Sunglasses as it asborbs ultraviolet preventing it from entering the eyes.
What does it mean if a wave is ionising?
it means that the wave is hazardous as it can kill cells or cause them to malfucntion resulting in premature ageing and diseases such as skin cancer.
What protects our skin from ultraviolet light?
Sunscreen as it absorbs ultraviolet light, preventing it from damaging the skin.
What are the two most ionising types of EM waves?
X-rays and gamma rays
Explain the harmful effects of X-rays & Gamma rays
As they’re highly ionising (due to high energy), they are able to penetrate the body and cause internal damage and cause the mutation of genes and cause cancer.
Why is the risk of X-rays very low?
The level of X-rays used in medicine is kept to minimum level, which is why the risk is very low.
How do doctors avoid unnecessary exposure to them by X-rays?
By leaving the room when taking X-rays in order to avoid unnecessary exposure to them
How do people working with gamma rays minimise their exposure? (and give an example)
People are routinely tested to check their radiation dose levels. For example, radiation badges are worn by medical professionals such as radiographers to measure the amount of radiation exposure in their body.
How can we see X-rays on X-Ray images?
X rays are absorbed by bones which is why we can see them on X ray images.
Which type of wave is a Wi-Fi signal?
Transverse
How can we send radio waves very long distances around the Earth?
Radio waves can reflect off a layer of charged particles in the atmosphere (the ionosphere), which allows us to send radio waves very long distances around the Earth.
How can microwaves communicate with satellites in space?
Microwaves can communicate with satellites in space due to the fact microwaves can pass through the Earth’s atmosphere without being reflected or refracted.
Why can we use infrared to cook food in ovens?
The energy of infrared is easily absorbed by the water molecules in food
What is a use for infrared cameras?
Infrared cameras can be used to check buildings for heat loss.
Explain optical fibres (for visible light)
Optical fibres are very thin strands of glass and we can transmit pulses of light down these fibres and use these pulses to carry information. They can be used to carry telephone and cable TV signals.
Why can light carry a great deal of information?
Light has a short wavelength
Why do we use ultraviolet (fluorescent) bulbs rather than visible light?
Because ultraviolet has a short wavelength, meaning it carries more energy than visible light.
How do fluorescent bulbs require less energy yet carry more energy than a bulb?
Energy of the ultraviolet is absorbed by the internal surface of the bulb and it is converted to visible light, requiring much less energy than a normal light bulb and as ultraviolet has a short wavelength, it carries more energy than visible light.
How can gamma rays and X-rays pass easily through body tissues?
They are both penetrative
Why can we see bones on X-ray images?
We can see bones on X-ray images, due to the fact X-rays are absorbed by bones.
Name one type of wave that is used in cancer treatment and explain what it does during the treatment.
Gamma-rays;
They ionise cancerous cells, causing them to die.
Precautionary measures to be taken with radio waves
None
Precautionary measures to be taken with microwaves
Make sure microwave oven door is tightly closed when in use
Precautionary measures to be taken with infrared
Eye sheilds/goggles/sunglasses
Precautionary measures to be taken with visible light
Wear sunglasses, or do not glare into very bright light
Precautionary measures to be taken with ultraviolet
Use of sunscreen or sunglasses that do not allow penetration of UV light
Precautionary measures to be taken with X-Rays
Use of lead screens, boxes around hospital machinery using X-rays. Wearing aprons to cover areas of body.
Precautionary measures to be taken with Gamma rays
Use of lead screens, boxes around hospital machinery using gamma rays. Wearing aprons to cover areas of body that gamma rays cause more damage.
Wavelength of the colour red in nanometres
700nm
Wavelength of the colour orange in nanometres
650 nm
Wavelength of the colour yellow in visible light in nanometres
570 nm
Wavelength of the colour green in nanometres
510 nm
Wavelength of the colour blue in nanometres
475 nm
Wavelength of the colour indigo in nanometres
445 nm
Wavelength of the colour violet in nanometres
400 nm
How will the ozone layer lead to an increased number of skin cancer in the future?
The ozone layer in the Earth’s atmosphere absorbs large quantities of the Sun’s UV radiation. There is real concern at present that the amount of ozone in the atmosphere is decreasing due to pollution. This may lead to increased numbers of skin cancers in the future.
Explain how a change in speed affects the wavelength of a wave.
Since frequency is the number of oscillations per second it is caused at the source of the wave and does not change;
So, as speed increases, wavelength increases
