AQA GCSE Physics Topic 4 Study Guide Exam And Correct Answers.
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Course
GCSE Physics
Institution
GCSE Physics
What was John Dalton's atomic theory? - Answer all matter is made of atoms that couldnt be broken down
What did JJ Thomson discover? - Answer discovered electrons that could be removed from atoms and he suggested that atoms were spheres of positive charge with tiny negative electrons insid...
AQA GCSE Physics Topic 4 Study Guide
Exam And Correct Answers.
What was John Dalton's atomic theory? - Answer all matter is made of atoms that couldnt be broken
down
What did JJ Thomson discover? - Answer discovered electrons that could be removed from atoms and
he suggested that atoms were spheres of positive charge with tiny negative electrons inside
What did Rutherford discover? - Answer by firing alpha particles at thin gold foil, he found that most
particles passed through and a few deflected back. This means that that most of the mass of the atom
must be concentrated at the centre in a tiny nucleu.This nucleus must also have a positive charge since it
reppelled the positive alpha particles. also found that most of the atom is empty space as they passed
straight through.
What did Neils Bohr discover? - Answer electrons can reside only on energy levels called orbitals or
shells
What did James Chadwick discover? - Answer Discovered the neutron which explains the imbalance
between the atomic and mass numbers
What is an isotope? - Answer Atoms of the same element that have different numbers of neutrons
What is radioactive decay? - Answer The process in which unstable isotopes decay into other elements
and emit ionising radiation as they attempt to become more stable
what are the three types of radio active decay? - Answer alpha, Beta , gamma
What is alpha radiation? - Answer When an alpha particle is emitted from the nucleus
-Alpha particles contain two neutrons and two protons
-not penetrative only travels a few cm in air but cannot pass paper
, -They are strongly ionising
What is beta decay? - Answer a type of radioactive decay in which an electron or a positron is emitted
from an atom.
-moderately ionising
-moderately penetrative so they can pas through air, paper but not by a sheet of aluminium
what is gamma decay? - Answer when gamma rays are released by the nucleus
-they are very penetrative and pass through anything but not lead or lots of concrete
-weakly ionising as they pass through
How can radiation be measured? - Answer with geiger-muller tube and counter which records the
count rate- the number of radiation counts reaching it per second
What is a half-life? - Answer the time taken for the radioactivity of a specified isotope to fall to half its
original value.
what can half life be used to find - Answer it can be used to find the rate at which a source decays
measured in becquerels,Bq (where 1 Bq is 1 decay per second)
how does the radioactivity of a source change over time? - Answer each time a radioactive nucleus
decays to become a stable nucleus, the activity as a whole will decrease
as time increases, the rate at which the source decays decreases
What does a short half-life mean? - Answer The activity falls quickly because the nuclei are very
unstable and rapidly decay. Sources with a short half-life are dangerous because of the high amount of
radiation they emit at the start - they quickly become safe though
What does a long half-life mean? - Answer The activity falls more slowly because most of the nuclei
don't decay for a long time - the source just sits there, releasing small amounts of radiation for a long
time. This can be dangerous because nearby areas are exposed to radiation for millions of years
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