Electromagnetic Waves Flashcards
Where does refraction take place?
At the bounties between layers of air at different temperatures
What is defraction?
The spreading out of waves when they pass through a gap or around an object
What are electromagnetic waves?
They are electric and magnetic waves disturbances that transforms energy from one place to another
What are the hazards/problems with using UV light?
Sun burns
Skin cancer
Why at night can you hear sound a long way away from its source?
Because sound waves refract back on the ground
What problems do infra-red course to cells?
Skin burns
What problems do micro and radio waves cause to cells?
Internal heating
Why can light not be diffracted around a corner?
Because the wavelengths are to small
How can we use information transferred?
By waves in communication
Give examples of electromagnetic waves?
Light waves
Radio waves
Microwaves
What is the change in direction due to (in refraction)?
A change of speed
What type of wave are electromagnetic waves?
Transverse waves
What is refraction?
The change in direction of waves when they travel across a boundary
Why is violet refracted the most ?
It has a shorter wavelength
What are gamma rays used for?
- to kill censer cells
- sterilise food so it doesn’t go of so quickly
- to check if two metals have fitted together
- to see inside your body
Give examples of mechanical waves
Sound waves
Water waves
Waves on spring and ropes
Seismic waves (produced by earthquakes)
How is UV light made?
Sun
Hot objects in space
Hot lights
What can infra-red be used for ?
Remote handsets
In optical fibers
Infra-red cameras
Infra-red scanned
What problems do UV, X-Ray and gamma rays cause to cell?
More servers cell damage
What are pixels?
Thousands of tiny light sensitive cells
When does the loudness of a note increase?
The amplitude of the sound waves increases
What can we use waves for?
- to transfer information
- to transfer energy
What is the wavelength?
The distance from one crest top to another
What are optical fibers?
They are very thin transparent fibers
They are used to transmit signals by light and infra-red radiation
What does white light contain?
All colours of the visible spectrum
What is the amplitude?
The height of the wave crest from the position of the rest
What are microwaves used for and why?
Satellite phone and tv links
They can pass through the atmosphere
Are mechanical waves transverse or longitudinal and give an example?
Both
Slinky spring
What are optical fivers used for?
Medical uses
Give three facts an image in a plane (flat) mirror
It is up right
Vertual
The same size as the object
What is the frequency if a humans hearing range?
20-20 000 Hz
Give all the electromagnetic spectrums from longest wavelength to shortest
Radio Micro Infrared Visible UV X-Ray Gamma
What does sound travel fastest through and why?
Solids because the particles are closer together
What are the hazards/problems with using light?
Bright light can cause discomfort
What do mechanical waves need to travel through?
A medium
What happens to the air when sound waves pass through it?
It makes the air around it vibrate as it pushes and pulls it
What is the frequency and what is it measured in?
The number of wave crests paras song through a point in one second
Hertz
Why do radio waves have poor reception when they go over hills?
Because they won’t have diffracted enough
Can sound diffract around an open door way?
Yes
When does the pitch note increase?
When the frequency of the found waves increase
What can electromagnetic waves do?
They can travel through a vacuum at the same speed of light (300000 kilometres per second) no medium is needed
What is the visible light used for?
Vision
Photography
What is the normal?
It is a construction line perpendicular to the reflecting surface at the point of incidence
Are mobile phones safe to use?
More research needs to be done to evaluate it
What are radio waves with more than 100m used for?
National and international radio stations
What are the hazards/problems with using radio waves?
It can course: cancer, effect health, cell damage, brain damage
What are the hazards/problems with using gamma ray?
Hard to control so you could kill other cells without meaning to
If exposed to it cells can mutate and cause cancer
It has a short wavelength so it is very dangerouse
What are x-rays used for?
To see bones in hospitals
What are mechanical waves?
They are vibrations that travel through the medium (substance)
What is the wave equation?
Speed (m/s)=frequency (Hz) + wavelength (m)
How are microwaves made?
Many types if transmitters
How are gamma rays made?
Some radioactive substances
Given of by stars
What is the hazard with using infrared?
Over heating
The warmer it is the …………. the spread of sound
Greater
What are echoes due to?
Sounds reflected of smooth hard surfaces
What is the difference between a real image and a virtual image?
A real image can be projected onto a screen but a virtual image can only exist in a mirror
For a light ray reflected by a plain mirror what two angles are there?
Angle of reflection
Angle of incidence
Why are radio waves with different wave lengths used for different purpose ?
Because the wavelength affects how far they go, how much they spread and how much information they carry
What are hazards with using X-rays?
They cause cancer if over exposed
What are UV lights used for?
Sun beds Lights Bugs are attracted to the light Fake notes They can glow in the dark so they are used in discos
How is light/visible made?
It is emitted by luminous objects
What are radio waves with a less than 1m wavelength used for?
TV broadcasting
What can we replace with radio waves?
Bluetooth
How are x-rays made?
X-ray machines
When light passes from air into glass is the angle of refraction (inside the glass) more or less than the angle of incidence?
Less
Why can’t light diffract around an open door?
Because the gap must be a similar size to the wavelength of the wave in order for diff reaction to take place
The greater the diffraction, the …………. the gap
Narrower
What are the hazard with using microwaves?
May stop working
Long exploiter can lead to brain damage
How are radio waves made?
Many transmitters
Lights
Stars
Sparks
What happens to sound during the day time any why?
Sound refracts upwards
Because the air near the ground is warmer than the air higher up
What are radio waves used for?
Radio and tv broadcasting
Radio communication
Mobil phone calls
What do microwaves carried ?
Mobile phone calls
What do we mean when we say that instruments resonates?
Vibration created by a musical instrument produces sound waves
