Cosmic rays (atomic nuclei stripped bare of their electrons) would continuously bombard Earth's surface if most of them were not deflected by earth's magnetic field. Given that earth is, to an excellent approximation, a magnetic dipole, the intensity of cosmic rays bombarding its surface is greatest at the

Options

A. Poles
B. Mid-latitudes
C. Equator
D. Mid-Longitude

Answer

To determine where the intensity of cosmic rays bombarding Earth's surface is greatest, we need to analyze the interaction between cosmic rays (which are primarily charged particles) and Earth's magnetic field.

### Step-by-Step Solution:

1. **Understanding Cosmic Rays**: Cosmic rays are high-energy particles, primarily protons, that travel through space. When they reach Earth, they can be deflected by magnetic fields due to their charge.

2. **Earth's Magnetic Field**: Earth behaves like a magnetic dipole, meaning it has a magnetic field with a north and south pole. The magnetic field lines emerge from the magnetic north pole and enter at the magnetic south pole.

3. **Deflection of Charged Particles**: When charged particles (like protons in cosmic rays) enter a magnetic field, they experience a magnetic force that can change their trajectory. The force experienced by a charged particle in a magnetic field is given by the equation:
\[ F = q(v \times B) \]
where \( F \) is the magnetic force, \( q \) is the charge of the particle, \( v \) is the velocity of the particle, and \( B \) is the magnetic field.

4. **Direction of Magnetic Force**: The direction of the magnetic force is perpendicular to both the velocity of the particle and the magnetic field. This means that as cosmic rays approach the Earth, they will be deflected by the magnetic field.

5. **Intensity of Cosmic Rays**: The intensity of cosmic rays bombarding the Earth's surface will depend on how effectively they are deflected by the magnetic field. The magnetic field is strongest at the poles, where the field lines are concentrated.

6. **Conclusion**: Since the magnetic field is strongest at the poles, the deflection of cosmic rays is also most significant there. Therefore, the intensity of cosmic rays bombarding the Earth's surface is greatest at the poles.

### Final Answer:
The intensity of cosmic rays bombarding Earth's surface is greatest at the **poles**.