Half life

Tick the boxes which are a correct unit for Activity

• s

• /s

• Bq

• J

Which is a good definition for half life?

• Time for half of the atoms to change to another element

• Time taken for half of the radioactive atoms to disappear

• Time taken for the activity of a sample to fall to one half of its initial value

The half life of a sample is 5 days. How many half lives have passed in a period of 15 days?

• 1

• 2

• 3

• 4

The half life of a sample is 2 hours. The initial activity is 4000Bq. What is the activity after 6 hours?

• 1000Bq

• 500Bq

• 250Bq

• I have no idea!

What is the half life of this sample?

• 2 mins

• 3 mins

• 4 mins

• 4 hours

Which graph has the shortest half life?

• red

• green

• dark blue

• light blue

A samples activity will fall from 10,000Bq to 1250 Bq in 12 years. What is the half life of the sample?

• 1 year

• 3 years

• 4 years

• 12 years

Tick the boxes which are true

• Half lives can be affected by temperature

• Half lives can not be changed at all by any physical variations

• Radioactive decay is random

• A radioactive isotope ca emit alpha and beta at the same time