Ch - 15 (Electromagnetic Spectrum) Flashcards by Khyati Upadhyay

What are the electromagnetic spectrum waves?

Radio waves
Microwaves
Infrared
Visible
Ultraviolet
X rays
Gamma rays

From longest wavelength (lowest frequency) to smalles wavelength and highest frequency.

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What’s re the effects of radiation with High energy?

Highly ionising
Harmful toc ells and tissue causing cancer.

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What is the effect of radiation with lower energy?

Useful for communications
less harmful to humans

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Define electromagnetic waves.

Transverse waves that transfer energy from the source of the waves to an absorber

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What are common properties of all waves?

They are all transverse
they can travel through vacuum
They all travel at same speed (3.0 x 10^8 m/s)

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What is radio used for?

Communication (radio or tv)

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what is the use of microwave?

Heating food
communication (WiFi, mobile phones, satellites)

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What is the use of infrared waves?

remote controls
-fibre optic communications
heating or cooking things
electrical heaters

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What is the use of visible light?

seeing and taking photo
fibre optic communication

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What is the use of ultraviolet rays?

Security marking
Fluorescents bulbs
Getting a suntan

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What is the use of x-rays?

X - Ray images (medicine)
Security checking

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What is the use of gamma rays?

Sterilizing medical instruments
Treating cancer

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What is the main use of radio waves?

Wireless communication and heating (very High intensities)

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What is the main use of infrared radiation?

security cameras (Used to illuminate an area without being seen, which is seen by detecting cameras)
Fiber optical cables
remote controls
emitted by warm objects

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What is the range of visible light wavelength that human can detect?

from 750 nanometers (red light) up to 380 nanometers (Violet light)

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What is ultraviolet responsible for?

giving a sun tan
When exposed, they absorb and re-emit it as visible light (also called fluorescence)

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What is fluorescence used for?

Used to make secretly mark things using special ink.
Light bulbs also use it

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What is the main use of X - rays?

Able go pass through most body tissues but are absorbed by denser parts of body (bone)
bones absorb the x - rays, leaving a shadow which can be seen when using a special x - Ray detector or photographic film.

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What is the main use of gamma rays?

Kill living cells and tissues
effective at destroying cancerous cells
sterilize food and medical equipment

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what EM waves are ionising?

Ultraviolet
x rays
gamma rays

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what happens as the frequency of EM waves increases?

Energy increases

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how does the danger associated with EM waves increase?

With frequency
Shorter the wavelength, the more ionizing the radiation
intensity of wave also plays a role

What is the danger of radio waves?

Nothing

What is the danger of microwave?

Possible heat damage to internal organs

What is the danger of infrared?

Skin burns

What damage is caused by visible light?

Bright light can cause eye damage

What is the danger of ultraviolet?

- Eye damage - Sunburn - Skin cancer

What is the danger of X - rays?

- Kills cells - Mutation - Cancer

What is the danger of Gamma rays?

- Kills cells - Mutations - cancer

Why does microwaves cause internal heating?

Absorbed by water molecules

What does ultraviolet result in?

Premature ageing, ionizing

What do X - rays and gamma rays do?

- penetrate through body and cause internal damage. - cause mutation of genes and cause cancer

What's re geostationary satellites used for?

Communicating information

What is the use of geostationary satellites or low orbit satellites?

- above earth's equator - orbit the satellites in 24 hrs - at a height of 36, 000 km higher than polar - used for radio and telecommunication

what is the characteristic of polar or low orbits satellites?

- orbit around North and south poles - 200km above sea level

What are the sues of polar satellites or low orbits?

- monitoring weather - much shorter time delay - signals and images are much clearer - limited use in any one orbit

What systems rely on long wave electromagnetic radiation?

- mobile phones, wireless internet & satellite television (using microwave) - Bluetooth, terrestrial television signals & local radio stations (using radio waves) - optical fibers (using visble or infrared waves)

What distance do radio waves transmit?

- Short distances - Terrestrial (local) television signals, radio stations transmissions

What wavelength are radio station signals transmitted at?

- longer wavelength than terrestrial television signals

In hilly areas does it receive terrestrial television signals or radio signals?

Radio signals because they are more prone to diffraction around the hills

Does Bluetooth use waves or wires?

Radio waves, over short distances.

What wavelength do Bluetooth signals have?

- shorter wavelength - enables High rates of data transmission, but can only be used for over short distances. - they can pass through walls but signals get weakens

What signals can microwave transmit?

- large distances - used to send signals to and from satellites -

What properties must the microwave have when transmitted from a dish?

- wavelength must be small compared to dish diameter to reduce diffraction - dish must be made of metal because metal reflects microwaves well.

Why do mobile phones and wireless internet use microwaves?

They are not refracted, reflected or absorbed by the atmosphere or ionosphere.

Which EM wave (s) do optical fibers use?

- visible light or infrared

Why do optical fibres use visible light and infrared?

- Glass is transparent to viable and infra - visible light have short wavelength, infrared can carry High rates of data due to high frequency.

What are the 2 types of signals?

Analogue Digital

Define analogues signals.

Vary continuously - they can take any value

Define digital signals

- can only take one of two (discrete) states - 1s and 0s - High and lows - On.s and off's

How are signals before and after?

Before transmission: Analogue to digital After transmission: Digital to analogue

What does analogue signal consist of?

Varying frequencies or amplitude. Ex - analogue technology include telephone transmission and some broadcasting.

What are the advantages of digital signal?

- signal can be regenerated so there is minimal noise - accurate signal, range of data signals is larger (they cover longer distances) - increased rate of transmission of data - extra data can be added to check for errors.