physics p4 Flashcards
what is half life?
time taken for half of the radioactive nuclei in a sample to decay
what is the activity?
the overall rate of decay of all of the radioactive isotopes in a sample
what is the activity measured in?
becquerels (Bq)
what is used to measure the radioactive decays per second?
geiger counter
what is a geiger counter?
used to measure the the radioactive decays (radiation emitted) per second
which electrons have the lowest energy in the atom
at the smallest distance from the nucleus
what is in the photon model
electromagnetic radiation is emitted and absorbed as energy (photons)
what is an alpha particle?
2 protons and 2 neutrons
(a nucleus of a helium atom)
what is a beta particle?
an electron
what is a gamma ray?
it is an electromagnetic wave so it doesn’t have a mass or charge
what happens in a beta decay?
a neutron decays to a proton and an electron
the electron is emitted as a beta particle
what number and symbols are used in an alpha nuclear equation?
4
He
2
what number and symbols are used in an beta nuclear equation?
0
e
-1
what happens in gamma decay?
gamma ray does not cause a change in mass or charge
what happens in neutron emission?
nuclei decays and produces large amounts of neutrons which then emit
what symbol and numbers are used in an neutron emission nuclear equation?
1
n
0
what is contamination?
when you take radioactive material inside your body or if it is on your skin. it cannot be removed once inside body
what is irritation?
when radioactive material is outside body but radiation can travel into the body
what can ionising radiation do?
can damage dna inside cells which causes cancer
what do unstable nuclei emit?
radiation:
alpha, beta, gamma, neutron
how do you detect radiation?
geiger-müller tube / geiger counter
how does the geiger counter detect radiation?
device clicks when radiation enters it. each click is a tiny current that produces when radiation ionises atoms inside tube
what are waves?
an oscillation that transfers energy
what are electromagnetic waves used for?
used to communicate between two phones
what type of wave is a sound wave?
longitudinal
what are transverse waves?
direction of the oscillations are perpendicular to the direction of the wave
what are longitudinal waves?
direction of oscillations are parallel to direction of the wave
how do you model waves?
using ripple on water waves to model transverse waves
how do you measure the velocity of waves?
a ripple tank
how do you use a ripple tank?
- motor vibrates bar, causing waves on surface of water
- image of waves are on screen underneath waves as light passes through it
how do you measure the velocity of sound?
- time how long it takes to hear an echo of a clap at a certain distance from the wall
- use an oscilloscope
what are the waves of the electromagnetic spectrum in order?
radio waves
micro waves
infrared
visible light
ultraviolet
x-ray
gamma ray
what do electromagnetic waves travel through?
a vacuum at 3.0 x 10^8 m/s
