A Radioactive Source Has a Half-Life of 2 Min $\times$ 10⁶
B)1

question 70

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 \(\times\) 10⁶
• B)1.67 \(\times\) 10⁶
• C)2.08 \(\times\) 10⁶
• D)3.41 \(\times\) 10⁶
• E)3.79 \(\times\) 10⁶

---

Definitions:

Social-cognitive Perspective

A view in psychology that focuses on how people process, store, and apply information about others and social situations.

Learned Helplessness

A condition in which a person suffers from a sense of powerlessness, arising from a traumatic event or persistent failure to succeed, and is characterized by giving up effort, even when opportunities for change are available.

Vulnerable

A state of being open to harm, damage, or attack, either physically or emotionally.

Creative Energy

The force or drive behind the generation of new ideas, artistic expressions, or problem-solving techniques.