Masses of atomic`//` subatomic particles are measured using a …………….. .

Answer

To answer the question regarding how the masses of atomic and subatomic particles are measured, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Context**:
- Atomic and subatomic particles include electrons, protons, neutrons, and other particles. Their masses are not directly measurable using traditional scales due to their extremely small size.

2. **Using Magnetic Fields**:
- When these particles are placed in a magnetic field, they exhibit specific behaviors. For instance, charged particles like electrons will move in circular or helical paths when subjected to a magnetic field.

3. **Cyclotron Motion**:
- The motion of a charged particle in a magnetic field can be described as cyclotron motion. The radius of the circular path (r) that the particle takes can be expressed by the formula:
\[ r = \frac{mv}{qB} \]
where:
- \( m \) = mass of the particle
- \( v \) = velocity of the particle
- \( q \) = charge of the particle
- \( B \) = magnetic field strength

4. **Measuring the Radius**:
- By measuring the radius of the circular path (r) that the particle takes in the magnetic field, along with knowing the values of the velocity (v), charge (q), and magnetic field strength (B), we can rearrange the formula to solve for mass (m):
\[ m = \frac{r \cdot q \cdot B}{v} \]

5. **Mass Spectroscopy**:
- Another method to measure the mass of atomic and subatomic particles is through mass spectroscopy. This technique allows for the analysis of the mass-to-charge ratio of ions, enabling the determination of their masses.

6. **Conclusion**:
- Therefore, the masses of atomic and subatomic particles are measured using techniques such as cyclotron resonance and mass spectroscopy.

### Final Answer:
Masses of atomic and subatomic particles are measured using a **mass spectrometer** or through **cyclotron resonance**.

---