• What is it? Even if there's no radioactive source around, a Geiger-Müller (GM) tube will still detect some ionizing radiation. This is our 'background radiation'.
• Location matters! The count rate from this radiation varies based on where the lab is located and the type of rock it's on.
• Why is it significant? We need to eliminate this background count when measuring radioactivity to get accurate results.
• Corrected Count Rate:
  • Formula: Corrected count rate = Observed count rate - Background count rate
  • Think of it as getting the pure juice after removing the pulp.

📌 Real-World Example: Imagine trying to hear a faint song in a room. But there's some random noise. To hear the song clearly, you'd want to subtract this noise.

• Both natural and artificial sources contribute.
• Example: Earth's rocks. They emit radon gas as their elements decay. This can pile up in buildings, but usually at safe levels!

• How to Use a Graph
  • Got a graph showing variation with time of corrected count rate from a sample? Use it to find the half-life!
  • Some graphs have scatter (random data points). This is expected in radioactivity experiments.
  • Estimate the time for the count rate to reduce by half. Do it three times from three different starting points. Take an average.
  • Mistake Alert!: Halving the count rate thrice will get you to 1/8 of the initial rate. Stick to the first or second half-life!

📌 Real-World Example: Imagine a cake that disappears half every day. If you start with a whole cake today, half will be left tomorrow, a quarter the next day, and so on.