6 end of the waves topic - lenses --> Flashcards
convex lenses
- shape of it bulges outwards
- light rays are speard out and then converge together and meet at the principle focus
concave lenses
- the sides cave inwards in a wierd shape
- light rays start together at the principle focus and then spread out when going through the lense
real image vs virtual image
REAL
- A real image is an image that can be projected onto a screen
- Rays of light actually pass through the image.
-
VIRTUAL
- cannot be projected onto a screen.
- It appears to come from behind the lens and can only be seen by looking through the lens.
what is white and black light
white light - all the diff colours put together - reflect all wavelengths of visible light equally
black - the absence of colour - absorbs all wavelengths of visible light
what is going on when something is OPAQUE
- either reflect or absorb all light that hits them.
- No light passes through.
colour filters
- filter different wavelengths of light so only certain colours are transmitted and the rest are absorbed
where is infrared radiation emitted from
the surface of an object
whats the trend between the temperature of an object and how much infrared radiation it radiates
the hotter the object the more infrared radiation it radiates
what happens when an object is HOTTER than its surroundings
hotter than surroundings = emits more IR than it absorbs and cools down
what happens when an object is COLDER than its surroundings
cooler than surroundings = absorbs more IR than it emits and warms up
results of the IR practcal - whats the best surface for IR
black matt
what are black body objects
- absorb all radiation that hits it
- no radiation is reflected or transmitted
- these are the best possible emitters
what happens on the black body radiation graph when the temperature increases
- temp increases = the intensity of every emitted wavelength increases
- the shorter the wavelength = the faster the intensity increases
how does radiation effect the earth temperatures during day and night
DAYTIME
- earth absorbs the suns radiation - temperatures increase
NIGHTTIME
- less radiation is being absorbed than emitted - decrease in local temperature
about sound waves
- caused by vibrating objects
- travels fastest in solids and slowest in gases
- ## when travelling through mediums the particles vibrate and therefore there is no sound in a vacuum bc no particles
parts of your ear
- ear drum
- ossicles
- semicircular canals
- cochlea
- auditory nerve - to the brain
how do you hear sound - process
- sound waves cause ear drum to vibrate
- these are passed through the ossicles then through the semicircular canals an then into the cochlea
- cochlea turns these vibrations into electricle signals when get sent to the brain
whats the human hearing range
20 - 20,000 Hz
what are ultrasound devices
- devices that produce electrical oscillations which convert to mechanical vibrations to produce sound waves above 20,000 Hz.
ultrasound in medical imaging
- ultrasound waves pass through the body and when they reach a boundary of different media some waves are reflected back and detected
- this exact timing is processed by a computer to creates images of the foetus
ultrasound in industrial imaging
- used to find flaws in pipes or woods or metal etc
- if there is a crack in these materials - the change in media will cause the waves to reflect sooner and therefore can be picked up by the ultrasound detector
p waves
- type of seismic wave
- happens inside the earth
- longitudinal
- travel through solids and liquids
- faster than s waves
s waves
- type of siesmic wave
- happens inside the earth
- transverse
- cant pass through liquids or gasses
- slower than p waves
translucent
- transmit light but the rays are SCATTERED.
- We cannot see objects clearly through translucent objects.
transparent
- transmit light WITHOUT scattering the rays.
- We can see objects on the other side of transparent objects.
