P1 Flashcards
(23 cards)
what is the angle of incidence?
the angle at which waves hit the medium
what is the angle of reflection?
the angle at which waves reflect off the medium
what is the law of reflection?
the angle of incidence is always equal to the angle of reflection
explain which way a wave bends depending on whether it is speeding up or slowing down
slowing down - bends towards the normal
speeding up - bends away from the normal
explain what effect the length of the wavelength (of the wave) or the size of the gap has on how much diffraction takes place
the longer the wavelength, or smaller the gap, the greater the diffraction
state a problem caused by diffraction
it can lead to loss of detail in images produced by microscopes and telescopes
what is total internal reflection?
when all of the light hitting a boundary is internally reflected e.g. if all light waves are moving in glass and hit a glass-air boundary, then if they are all reflected back into the glass, TIR will have occured
state the 2 conditions needed for TIR to occur
- the angle of incidence is greater than the critical angle
2. the waves are moving in the denser of the 2 materials
explain what happens to light as it passes along an optical fibre
the light is reflected along the optical fibre at an angle greater than the critical angle, so the waves travel along the fibre by total internal reflection
explain 2 uses of fibre optics
- fibre optic broadband - pulses of visible light or infrared are sent down optical fibres, allowing lots of data to be transmitted quickly
- endoscope - a key-hole incision is made in the body and the endoscope is inserted into it. The endoscope contains several bundles of optic fibres. Light is sent down one of the bundles, illuminates the inside of the body, and is then reflected back down another bundle. This illumination allows the doctor to see inside the body.
state 3 uses of lasers
- surgery
- guiding weapons
- CD/DVD players
- cutting materials
state 3 properties of laser light
- monochromatic
- low divergence
- light is in phase (waves are in sync - crests and troughs line up)
describe how laser light is used in a CD player
- the cd has a shiny surface with pits and lands, and spins in the player
- a laser reflects from its surface. When the laser enters a pit, it doesn’t reflect back
- this forms a series of light pulses which are converted into sounds or images by a computer chip
state 3 factors that can cause a loss in signal when using microwaves. Explain why these factors cause signal loss
- poor weather conditions (scatter signals, making them difficult to receive
- large surfaces of water (also scatter signals)
- curvature of earth (can get in the way of line of sight)
- hills and buildings (gets in the way of line of sight)
- other EM waves can interfere with microwave signals
state 2 benefits of using digital signals over analogue ones
- because a digital signal can only be 1 or 0, it is easy to detect and remove noise, improving sound or image quality
- multiplexing - many digital signals can be sent at once, so more information can be sent at once
state 2 advantages and 2 disadvantages of the use of DAB radio
advantages:
- more stations available
- less chance of interference with other stations so clearer signal
disadvantages:
- may not cover all areas of the UK
- sound quality may not be as good as FM due to the sound being compressed (e.g. MP3 files)
state and explain a disadvantage of using wireless signals
wireless signals may reflect off many different surfaces. This can lead to a drop in quality because the signals lose energy with every reflection/refraction
state and describe 2 ways in which wireless signals can be sent over long distances
- radio waves can be reflected off the ionosphere by TIR
2. satellites can receive and re-transmit microwave signals to another receiver
describe simply how earthquakes happen
plates slip along the fault lines
state the 2 types of seismic waves, and 2 of their differences
- p-waves: travel through both solid and liquid - longitudinal waves
- s-waves: travel through only solid - transverse waves
explain how seismic wave data is recorded and how it may indicate features of the structure of the earth
- seismic waves are detected using seismometers, which produce seismographs
- after an earthquake, s-waves are only detected in certain areas, showing that the earth has a molten (liquid) outer core
state a problem caused by ultraviolet radiation
skin cancer
explain how dark skins have a lower cancer risk
more UV radiation is absorbed at the surface, protecting sensitive cells underneath
