Topic 5 - Light and the EM spectrum Flashcards
Angle of incidence=
Angle of reflection
Total internal refelction occurs when
The wave is travelling through a dense material into a less dense material. When the angle of incidence is larger than the critical angle.
Specular reflection
When waves are reflected in a single direction by a smooth surface.
Diffuse reflection
When waves are reflected in all directions by a rough surface because the normal is different for each incident ray
All different colours of light have
Different wavelengths
Opaque objects
Dont transmit light
White objects
Reflects all wavelengths of light equally
Black objects
Absorb all wavelengths of light
Transparent and translucent objects
Transmit light
Coverging lenses
Bulge outwards in the middle and causes rays of light to converge together at the principal focus
Diverging lenses
A diverging lens caves inwards and causes rays of light to spread out
Principal focus on converging lenses
Where the rays meet after being refracted through the lens
Principal focus on diverging lens
Where the rays meet if thye get traced backwards through the lens. It is before the lens.
Focal length
The distance from the centre of th lens to the principal focus
A real image is
When the light rays actually come together to form the image.
A virtual image is
when light rays from the object appear to be coming from a different place to where they are coming from.
Real images are usually created by
Converging lenses
Virtual images are usually created by
Diverging/convex lenses
Electromagnetic waves are
Transverse
EM waves travel at
the same speed through a vacuum, but have different speeds in different materials.
All EM waves transfer energy from
A source to an absorber
Example of source to absorber in EM waves
When near an electric heater, infrared waves transfer energy from the heaters thermal energy store to your thermal energy store
Types of EM waves in order of wavelength
Radio waves
Microwaves
Infrared
Visible light
Ultra Violet
X-Rays
Gamma Rays
The EM spectrum is in order of
Decreasing wavelength and increasing frequency
The higher the frequency of an EM wave
The more energy is transfers (so it is more dangerous for humans)
EM waves at a boundary can
Be absorbed, reflected, refracted, or transmitted
Radio waves are … through the body
transmitted
Some wavelengths of microwaves can be…. by bodily cells
Absorbed
Infrared and visible light are mostly ….or…. by the skin
Reflected or absorbed
Ultraviolet is … by the skin and is slightly …..
Absorbed, ionising
Colours of visible light in order of decreasing wavelength
Red
Orange
Yellow
Green
Blue
Indigo
Violet
All bodies and objects constantly
Absorb and emit EM waves
The intensity and distribution of the wavelengths of EM emission depend only on
Temperature
For an object to be at a constant temp
It needs to radiate the same avergae power as it absorbs
Radiation effects the earths temperature by
Absorbing during the day fro mthe sun, and emitting from the atmosphere during the night
Steps of core practical investigating how surfaces emit radiation
Use 4 test tubes wrapped in the same material but with different surfaces
Add boiling water and measure how quickly temperature decreases using a thermometer
Microwaves can lead to
Internal heating of humans
Infrared can lead to
Skin burns
Ultraviolet can lead to
damage to surface cells such as skin and eyes, which leads to skin cancer and eye conditions
X-rays and gamma can lead to
Mutation or damage to deeper tissues
Radio waves are used in
Broadcasting
Communications
Satellite transmissions
Microwaves are used in
Cooking
Communications
Satellite transmissions
Infrared is used in
Cooking
Thermal imaging
Short-range communications
Optical fibres
TV remotes
Security systems
Visible light is used for
Vision
Photography
Illumination
Ultraviolet is used for
Security marking
Flourescent objects and lights
Detecting forged bank notes
Disinfecting water
X-rays are used for
Observing the internal structure of objects
Medical x-rays
Airport security scanners
Gamma rays
Sterilising medical equipment and food
Detection fo cancer
Cancer treatment
Radio waves can be produced by or induce
Oscillations in electrical circuits from a transmitter or at a receiver
Changes in atoms and nuclei can lead to or be caused by
Can lead to radiation being generated over a wide frequency range
Can be caused by absorbtion of different radiations
Changes in the nucelus itself leads to the production of gamma rays
