Topic 1: Technical Skills

Question 1

Describe what physicists mean by the terms accuracy and precision (2)

Answer 1

• Accuracy is (a measure of) how close a
  measured/calculated value is to the true value
• Precision is (a measure of) the consistency of values obtained by repeated measurements

Question 2

Describe the procedure she should follow to determine an accurate value for the
external diameter of the tube. (3)

Answer 2

• (Take readings at) different places/positions
• (Take readings at) different orientations/angles
• Calculate a mean/average value

Question 3

A student used a GM tube to measure activity of a radium source (emits α, β, γ radiation) at 20cm distance. He took two 1-minute counts (183, 178) and calculated the mean (181). Criticise this method for determining the count. (3)

Answer 3

• Counting for 1 minute is too short a time
  {Or he should count for at least 3 minutes}
• He hasn’t recorded the background count rate
• More than one reading taken and a mean calculated {Or should have taken more than two readings (to
  calculate mean)}