P1 - topic 2 - visible light, UV, X-rays Flashcards
why do we see objects?
because they either give out or reflect light - they’re illuminated
When light enters your eye, what happens?
light gets refracted through the lens and focused onto the retina at the back of the eye. The retina sends messages to the brain and the brain interprets them
How do cameras work?
use a lens to focus visible light onto a light sensitive film or electronics sensor that records the image
What controls how much light enters the camera?
The Lens aperture
What does the shutter speed on a camera determine?
how long the film or sensor is exposed to the light
What two things control how much light the photographer can capture
shutter speed
Aperture
what radiation is used to detect forged bank notes?
ultra violet
what is a property of certain chemicals?
florescence
why are things fluorescent?
ultraviolet radiation is absorbed and then visible light is emitted
why do bank notes print special marking in fluorescent ink of their bank notes?
to detect forgeries
how can you tell the difference between a genuine bank not and a fake bank note?
using a ultra violet light,
genuine notes will display the special fluorescent markings
fake notes will glow all over and there’ll be no markings
on fake bank notes why do they glow all over and show no markings when under a UV light?
they are often printed on cheaper paper that’s slightly fluorescent
How do fluorescent lamps use UV radiation?
they use it to emit visible light
why are fluorescent lamps safe to use?
all the UC radiation is absorbed by a phosphor coating on the inside of the glass
Why are security pens used?
to mark your property with your name
how do security pens work?
the ink in the pen is only visible in UV light so it can help the police identify your property of its stolen
Why is UV radiation used to disinfect water?
the UV kills off any viruses and bacteria in the water to make it safe to use
What are the four main uses of UV radiation?
Bank notes
Fluorescent lamps
Security pens
Disinfect water
what are X rays used for?
looking inside objects
what do radiographer a on hospitals do?
take X ray photographs of people to see if they have any broken bones
why do we need viable light?
so that we can see
what do X rays pass through easily?
flesh
what do X rays not travel through easily?
more dense materials than flesh like bones or metal
what give you an X Ray image?
the amount of radiation that’s absorbed or not absorbed
what can X rays cause?
cancer
what do radiographers do to prevent them from cancer?
wear lead aprons and stand behind a lead screen or leave the room to keep their exposure to X rays to a minimum
why do airport security use X rays?
to scan luggage to check for suspicious-looking objects
why do airports use low-level X rays?
because they aren’t as harmful as the X rays used in hospitals
