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PHYSICS, M8 2024 HSC 7 MC

A pure sample of polonium-210 undergoes alpha emission to produce the stable isotope lead-206.

The half-life of polonium-210 is 138 days.

At the end of 276 days, what is the ratio of polonium-210 atoms to lead-206 atoms in the sample?

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→ After two half-life’s of the polonium only one quarter of the sample of polonium-210 atoms will be left.

→ Therefore, three quarters of the polonium-210 atoms would have decayed into lead-206 atoms.

→ The ratio of polonium atoms to lead atoms is

♦ Mean mark 45%.

PHYSICS, M8 2023 HSC 11 MC

The chart shows part of a nuclear decay series beginning with uranium.
 


 

Which option correctly identifies and and the process by which each was produced?

 

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→ During the decay process producing , the Atomic number decreases by 2 to 90 and the Mass number decreases by 4 to 234

→ Alpha decay producing 

→ During the decay process producing , the Atomic number increases by 1 to 91 and the Mass number does not change. 

→ Beta decay producing

PHYSICS, M8 EQ-Bank 23

A patient is given an injection containing kg of radioactive technetium-99m which has a half-life of 6 hours.

How much remains undecayed when a scan is taken 3 hours later?   (3 marks)

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Calculating the decay constant:

 
   
   

 
Amount remaining undecayed:

 
   
   
   

PHYSICS, M8 EQ-Bank 3 MC

A 5-gram sample of radioactive strontium-90 decayed over time. The graph shows the mass of strontium-90 remaining from the initial sample as a function of time.
 

What is the approximate value of the decay constant, in , for strontium-90?

  1. 0.006
  2. 0.011
  3. 0.014
  4. 0.025
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→ From the graph, the half life (mass = 2.5 g) is approximately 29 years.

 
   
   

 

PHYSICS M8 2022 HSC 24

The radioactive decay curve for americium-242 is shown.
 


 

  1. Use the graph to find the half-life of Am-242 and hence show that the decay constant, , is   (2 marks)
  1. Calculate how long it takes until the mass of Am-242 is 8 micrograms.  (2 marks)
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a.   

b. 

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a.   The half life of Am-242 is 16 hours.

 
   
   

 

b.    
     
 
 
     
   

PHYSICS, M8 2021 HSC 35

A spacecraft is powered by a radioisotope generator. Pu-238 in the generator undergoes alpha decay, releasing energy. The decay is shown with the mass of each species in atomic mass units,

  1. Show that the energy released by one decay is  J.   (3 marks)
  1. At launch, the generator contains    atoms of Pu-238. The half-life of Pu-238 is 87.7 years.
  2. Calculate the total energy produced by the generator during the first ten years after launch.  (3 marks)
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a.   

 
 

  

   

b.  


♦ Mean mark part (b) 51%.

PHYSICS, M8 2021 HSC 19 MC

Rh-106 is a metallic, beta-emitting radioisotope with a half-life of 30 seconds.

A sample of Rh-106 and an electrode are placed inside an evacuated chamber. They are connected to a galvanometer and a variable DC power supply.
 

A student measures the current, , when the power supply is set to zero. They then measure the stopping voltage, . The stopping voltage is the minimum voltage needed to prevent current flowing.

A few minutes later, these measurements are repeated.

How do the TWO sets of measurements compare?

  1. Only changes.
  2. Only changes.
  3. Both and change.
  4. Neither nor changes.
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Due to the short half life of the isotope, there will be significantly less present when the second reading is made.

→ Lower rate of emission of electrons → Lower recorded current

The energy of emitted electrons will remain the same → Voltage will not change


♦ Mean mark 29%.