Past Papers Wrong Answers

Question 1

Explain how an uncharged object may become positively charged

Answer 1

Negatively charged electrons transferred from the neutral object

Question 2

Why is the radioactive decay model good

Answer 2

Cannot predict which… will decay

Cannot predict when….will decay

Question 3

Why should you use protection from radioactive substances

Answer 3

Prevent contamination

Which would cause damage over a longer time period

Question 4

Why does the alarm switch on when the smoke particles enter the plastic casing

Answer 4

Smoke stops alpha radiation

Question 5

Explain why the radiation source inside the smoke alarm should have a long half life

Answer 5

How long half life means the count rate is constant

Question 6

Explain the ideal properties of a radioactive source for use in medical diagnosis

Answer 6

short half-life or half-life of a few hours
• (short half-life means) less damage to cells / tissues / organs /
body
• low ionising power
• (low ionising power means) less damage to cells / tissues /
organs / body
• highly penetrating
• (highly penetrating means) it can be detected outside the body
• emits gamma radiation

Question 7

Why is radiation in body dangerous

Answer 7

Highly ionising, increased risk of cancer, until radioactive material is removed

Question 8

A sample of polonium-210 was left for 414 days. After this time it had a mass of 1.45 × 104 g The half-life of polonium-210 is 138 days.

Calculate the initial mass of the sample.

Answer 8

414/ 138 = 3 half lives

1. 45x 10 ^-4. x 2 x 2 x 2
2. 16 x 10 ^-3

Question 9

Force acting on static balloon and hair

Answer 9

Non- content attraction