The half life of a substance is 20 minutes. E The time interval between 33% decay and 67% decay.

Explanation

To solve the problem, we need to find the time interval between 33% decay and 67% decay of a substance with a half-life of 20 minutes. We will use the decay constant and the formula for exponential decay.

### Step-by-Step Solution:

1. **Determine the Decay Constant (λ)**:
The decay constant (λ) can be calculated using the formula:
\[
λ = \frac{0.693}{t_{1/2}}
...