P1 topic 2 Flashcards
how uv lamps produce light?
they produce uv light when mercury vapour conducts electricity
which part of the EM spectrum can be used to sterilise water?
ultraviolet
what are photos taken with infrared called?
thermographs
how so security systems detect an intruder?
they detect the infrared waves emitted by an intruder
Why is glass used over copper for optical fibres?
it’s lighter and cheaper- they can also transmit the information much faster
how can x rays be produced?
fast moving electrons are fired at a metal plate- x rays can be used to detect an object’a internal structure
how does a Geiger-muller tube work?
when an alpha/beta particle enters the tube, it ionises the gas inside- this produces a pulse of electrical charge, which is detected by the counter attached to the GM tube- each click or count represents one particle being detected
What does a Geiger-muller tube detect?
ionising radiation
ionisation
all types of radiation transfer some of their energy to the atoms of the material they are passing through- when this happens, electrons can get knocked off the atom to form a positive ion
what are distances in the solar system measured in?
astronomical units- 1 AU is the average distance from the earth to the sun
how do microwaves cook food?
the microwaves are absorbed by the water and fat in the food, and the energy becomes heat
radio waves
they are produced and detected by aerials- they are used it broadcast TV and radio programmes and by emergency services for communication
microwaves
very high frequency radio waves- used to cook food in a microwave oven and for mobile phone communication
how do high frequency radio waves and microwaves travel?
in straight lines to satellites- mobile phone networks use satellites to transmit communications around the world at high speeds
why do satellite dishes need it be pointed directly at the satellite?
satellite TV is broadcast using very short wavelength radio waves, so satellite dishes need to be pointed directly towards the satellite
