A Radioactive Source Has a Half-Life of 2 Min

question 61

Multiple Choice

A radioactive source has a half-life of 2 min. At time t = 0 it is placed near a detector and the counting rate is observed to be 3000 counts/s. If the detection efficiency is 25%, how many radioactive nuclei are there at time t = 2 min?

• A) 1.04 × 10⁶
• B) 1.67 × 10⁶
• C) 2.08 × 10⁶
• D) 3.41 × 10⁶
• E) 3.79 × 10⁶

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Definitions:

Framing

The way in which information is presented to influence perceptions, decisions, and judgments; often used in contexts of communication and psychology.

Nudge

A framing of choices by which governments and companies can, without coercion or altered incentives, encourage people to make choices that support their health, retirement savings, and well-being.

Choices

The act of selecting between two or more possibilities when faced with a decision.

Belief Perseverance

The phenomenon wherein individuals maintain their beliefs even in the face of contradictory evidence.