Which statement is incorrect?

Options

A. `alpha`- rays have more penetrating power than `beta`-rays
B. `alpha`- rays have less penetrating power than `gamma`- rays
C. `beta`-rays have less penetrating power than `gamma`-rays
D. `beta`-rays have more penetrating power than `alpha`-rays

Answer

To determine which statement is incorrect regarding the penetrating power of alpha rays, beta rays, and gamma rays, we can analyze the properties of each type of radiation.

### Step-by-Step Solution:

1. **Understanding the Types of Rays**:
- **Alpha Rays**: Composed of helium nuclei (2 protons and 2 neutrons), alpha particles are relatively heavy and positively charged. They have low penetrating power and can be stopped by a sheet of paper or a few centimeters of air.
- **Beta Rays**: These are high-energy, high-speed electrons or positrons emitted by certain types of radioactive nuclei. Beta particles are lighter than alpha particles and can penetrate further, typically being stopped by a few millimeters of plastic or a few centimeters of aluminum.
- **Gamma Rays**: These are electromagnetic radiation of high frequency and energy. Gamma rays have no mass or charge, allowing them to penetrate materials much more effectively than both alpha and beta rays. They require dense materials like lead or several centimeters of concrete to be effectively blocked.

2. **Evaluating the Statements**:
- **Statement 1**: "Alpha rays have more penetrating power than beta rays."
- This statement is **incorrect**. Beta rays have more penetrating power than alpha rays.
- **Statement 2**: "Alpha rays have less penetrating power than gamma rays."
- This statement is **correct**. Gamma rays have the highest penetrating power.
- **Statement 3**: "Beta rays have less penetrating power than gamma rays."
- This statement is **correct**. Gamma rays penetrate more than beta rays.
- **Statement 4**: "Beta rays have more penetrating power than alpha rays."
- This statement is **correct**. Beta rays penetrate more than alpha rays.

3. **Conclusion**:
- The incorrect statement among the options provided is **Statement 1**: "Alpha rays have more penetrating power than beta rays."

### Summary:
The statement that is incorrect is that alpha rays have more penetrating power than beta rays.