The velocity of `alpha`-rays is approximately

Options

A. Equal to that of the velocity of light
B. 1/10 of the velocity of light
C. 10 times more than the velocity of light
D. Uncomparable to the velocity of light

Answer

To determine the velocity of alpha rays, we can follow these steps:

### Step 1: Understand what alpha rays are
Alpha rays consist of alpha particles, which are essentially helium nuclei. An alpha particle can be represented as \( \alpha \) or \( ^4_2He \), where 4 is the mass number and 2 is the atomic number.

### Step 2: Determine the characteristics of alpha particles
Alpha particles are relatively heavy compared to other types of radiation (like beta particles or gamma rays). Their mass contributes to their overall behavior in terms of velocity and penetration power.

### Step 3: Analyze the velocity of alpha particles
The velocity of alpha particles is not very high due to their mass. It is known that the velocity of alpha particles varies from approximately one-tenth to one-twentieth of the speed of light.

### Step 4: State the range of velocity
Thus, the approximate velocity of alpha rays can be stated as:
- **Velocity of alpha particles**: \( \frac{1}{10} \) to \( \frac{1}{20} \) the speed of light.

### Step 5: Conclusion
Given the information, we conclude that the velocity of alpha rays is approximately:
- **Answer**: \( \frac{1}{10} \) to \( \frac{1}{20} \) of the speed of light.