Mid term prepaation

An α-particle and a β-particle have the same kinetic energy.

Why does the α-particle have a larger ionising effect than the β-particle as it passes through air?

• The α-particle has a larger charge and a larger velocity so is closer to an air particle for a shorter time.
  

• The α-particle has a larger charge and a smaller velocity so is closer to an air particle for a longer time.
  

• The α-particle has a smaller charge and a larger velocity so is closer to an air particle for a shorter time.
  

• The α-particle has a smaller charge and a smaller velocity so is closer to an air particle for a longer time.
  

A student is carrying out an experiment to measure the radiation from a radioactive source.He uses a radiation detector and records the total counts in 5-minute intervals. He does this three times with the source present and three times with the source absent. Here are his results.

What is the average corrected count rate for the source?

• 5 counts / minute

• 9 counts / minute

• 25 counts / minute

• 45 counts / minute

The count rate measured near a radioactive source drops from 542 counts per minute to 94 counts per minute in 12 hours. The background count remains constant at 30 counts per minute.

What is the half-life of the source?

• 2 hours

• 3 hours

• 4 hours

• 8 hours

The products of the decay of a nucleus of a radioactive isotope are a nucleus and radiation which is emitted.

What is the nature of the products?

• a nucleus of an element different from the isotope is formed and both an α-particle and γ-radiation are emitted
  

• a nucleus of an element different from the isotope is formed and just γ-radiation is emitted
  

• a nucleus of the same element as the isotope is formed and both a β-particle and γ-radiation are emitted
  

• a nucleus of the same element as the isotope is formed and just an α-particle is emitted
  

An atomic nucleus decays by one or more radioactive decay processes. What causes the proton number to decrease by 1?

• α-decay followed by β-decay

• α-decay only

• β-decay followed by γ-decay

• β-decay only

Which definition of half-life is not correct?

• the time it takes for the count rate from a radioactive sample to fall to half its original value

• the time it takes for half of the unstable nuclei in a radioactive sample to decay

• the time it takes for the mass of radioactive material in a sample to halve

• the time it takes for half of the neutrons in a radioactive sample to decay

A scientist fires alpha-particles at a very thin sheet of gold and detects the particles that pass through. Which statement about the results of the scattering experiment is correct?

• Alpha-particles are attracted to the nucleus of the atoms in the metal sheet.

• Half the mass of the atom is concentrated in the nucleus.

• Most of the alpha-particles are deflected, showing that the nucleus is very dense.

• Only a small number of alpha-particles are deflected, but some of these are deflected through large angles.

The notation represents the nucleus of a gold atom.

The relative charge on a proton is +1. What is the relative charge on the gold nucleus?

• +79

• +118

• +197

• +276

An isotope of hydrogen has the nuclide notation:

How many neutrons are in the nucleus of this isotope and what is the relative charge on the nucleus?

'number of neutrons' (a)   ​

'relative charge' ​ (b)  

• 2
• +1
• +2
• 1

The reading on a detector placed near a radioactive material is 536 counts per second. The background count rate is 44 counts per second. The half-life of the radioactive material is 34 hours. What is the reading on the detector after 68 hours?

• 44 counts per second

• 123 counts per second

• 134 counts per second

• 167 counts per second