Chapter 13: Electromagnetic Waves Flashcards
(22 cards)
Give the order of the electromagnetic spectrum in order of decreasing wavelength and increasing frequency and energy.
- Radio waves
- Microwaves
- Infrared radiation
- Visible light (red to violet)
- Ultraviolet waves
- X-rays and gamma rays
What units are used to measure the wavelengths of waves on the electromagnetic spectrum?
- Kilometre
- Millimetre
- Nanometre
- Picometre
What can the human eye only detect?
Visible light.
Give the wavelength of visible light.
Around 400nm to 700nm
What speed do electromagnetic waves travel at?
300 million m/s through space or in a vacuum
Give the equation for wave speed.
v=fλ (wavespeed(m/s)=Frequency(Hz)xWavelength(m))
What does white light contain?
All the colours of the visible spectrum.
Does the wavelength across the spectrum from violet to red increase or decrease?
Increase.
If an object is hotter, does it produce more or less infrared radiation?
More.
What is infrared radiation used for?
- Optical fibres.
- Transmitting signals from TV handsets.
- Scanning in medicine, hot spots on body surface could have unhealthy tissue.
- Infrared cameras.
- Electric heaters.
- Electric cookers.
What are microwaves used for?
- Communications, eg satellite TV (microwaves pass through the atmosphere and reach satellites).
- Microwave ovens- heat food faster than regular ovens because microwaves penetrate into food and are absorbed by the food’s water molecules.
What are radio waves used for?
-Wireless connections (ie Bluetooth).
Why can microwaves and radio waves be hazardous?
- They penetrate people’s bodies.
- They can hit internal parts of the body.
What does the wavelength of radio waves affect?
- How far they can travel.
- How much they spread.
- How much information they can carry.
Shorter wavelength=
- More information.
- Shorter range.
- Less spread out.
Why are microwaves used for satellite and TV signals?
- They can travel between satellites.
- They spread out less than radio waves, so do not lose their signal as much.
What are radio waves less than 1 metre used for and why?
- TV broadcasting from TV masts.
- This is because they can carry more information than longer radio waves.
What are radio waves between 1-100 metres used for and why?
- Used by local radio stations.
- Used by emergency services.
- This is because their range is limited to the area around the transmitter.
What are radio waves over 100 metres used for and why?
- Used by national and international radio stations.
- This is because they have a much longer range than shorter-wavelength radio waves.
What are optical fibres and what are they used for?1
- Very thin transparent fibres.
- Used to transmit communication signals by light and infrared radiation.
Can UV waves harm the skin and the eyes?
Yes.
What are gamma rays used for?
- Killing harmful bacteria in food.
- Sterilising surgical equipment.
- Killing cancer cells.
