Chapter 12 And 13 -Using Waves And Light Waves Flashcards
What happens when wavelength increases
Frequency decreases
Name the 7 types of em waves in order of short to long wavelength
Gamma rays, X-Ray’s, ultraviolet,visible light, infra red, microwaves , radio waves
Harmful effects of microwaves
Can penetrate all body tissues and are absorbed by cytoplasm of living cells.
Causes body to overheat, if temperature increases too much body cells may die
Harmful effect of infra red waves
Over exposure can burn the skin
Harmful effects of ultra violet waves
Can be dangerous to our bodies. Much of the Suns ultraviolet rays are absorbed by the ozone layer.
If our bodies receive too much of this light skin can burn (sunburn) - can develop into skin cancer.
Too much uv waves an damage the human retina and can cause blindness
Harmful effects of x Ray’s waves
Can cause cancer if over exposed due to cell damage
Harmful effects of gamma rays
Cells can be destroyed or mutated
Can cause cancer
6 properties of EM waves
- All are transverse waves
- Transfer energy from one place to another
- Can travel through a vacuum
- Travel at the same speed.
- Consist of oscillating electric and magnetic fields
- Can be reflected, refracted and diffracted
Uses of radio waves
Radio transmitters
Tv transmitters
Uses of microwaves
Microwaves
Ovens
Mobile phone communication
Satellite
Uses of infra red waves
Infra red cookers and heaters
Tv and stereo remote controls
Night vision
IR cameras - detect cancer
Uses of visible light
Safety clothing Lasers - barcode scanners, CD rooms, optical fibres, military for guiding missiles Telecommunication Sensors Endoscopes
Uses of UV waves
Florescent tubes
UV scanning lamps
Washing powder
Uses of X Ray’s
X-radiography to observe the internal structure of objects
Uses of gamma rays
Sterilise food and medical objects
Cancer treatment
What do digital signals do
Converts info into binary code (0 and 1)
Converted into electrical pulses that are sent down a telephone line
What do analogue signals do
Info is converted into electrical signals/ currents that vary continually
Signals are amplified and sent into a loud speaker
4 advantages of digital signals
- All signals become weaker in transmission - needed to be amplified / regenerated
- Regeneration in digital signals makes a clean copy of original. In analogue the background noise is also amplified causing original to be drowned out or include errors when info is carried
- Digital systems are easier to design and build
- Digital systems deal with data that is easy to process
Why are tv and radio broadcasted with digital signals nowadays
Takes a wide range of frequencies to broadcast analogue signals
Using digital means more programmes can be broadcasted over the same frequenseies
What is optical fibre communication
Extremely pure glass is used to transmit infra red and light waves carrying large amounts of info and data
The light is continually reflected (total internal reflection ) along the fibre and is very secure
What is cataract
When an eye becomes cloudy you cannot see out of it due to light not being able to enter the eye correctly
Now you can remove the damaged part and replace it with a clear plastic that will allow light to enter the eye
Define luminous objects
Objects that emit light e.g. The sun
Define non luminous objects
Objects that reflect light e.g. A book
How does a periscope work
Uses two mirrors to change the direction of Ray’s of light
Rays from the mirror stake first mirror at angle of 45 degrees to the normals
The rays are reflected 45 degrees to the normal and are turned through an angle of 90 degrees.
Changing the direction of Ray’s of light in this way allows an observer to use a periscope to see over and around objects
Properties of an image in a plane mirror
Image is a far behind the mirror as the object is infront.
Image is same size as the object
Image is virtual, cannot be produced on a screen
Image is laterally inverted / reversed
Image is upright
What happens when a ray of light crosses a boundary of a different medium
If it enters a denser medium it will slow down causing the Ray to change direction and it is refracted towards the normal
If it enters a less dense medium it will do the opposite
How do we see images in a mirror
Image is formed as Ray’s of light from an object hit the mirror
These rays are reflected back into eyes and brain interprets it
Define virtual
Image in a plane mirror is a virtual image and the same size as the object
What causes the dispersal in a prism with a rainbow
- when each of the light colours have a different wavelength and speed in the medium
- all colours have the same speed in a vacuum
- when light enters the glass the different coloured lights slow down and are refracted
- as each colour of light slows down a specific amount of the colours will be refracted though different angles
What’s smells law
That the refractive index of a medium can be calculated from the angles of incidence and refraction
N = sin i
—–
Sin r
What is total internal reflection
Can only Oxus when a ray of light travels from a medium with higher refractive index and the angle of incidence is greater than the critical angle
What is an optical fibre
A thin rod of high quality glass
Very little light is absorbed by this glass
Light gets in at one end does repeated internal refraction and emerges at the other end
Works when fibre emerges at other end
What is a real image
E.g. A movie on a cinema screen
Formed by real rays that meet at a point and can be projected onto a screen
What is a virtual image
E.g. In a mirror
Formed by imaginary rays and cannot be projected onto a screen
