A proton and a deuteron having equal momenta enter in a a region of a uniform magnetic field at right angle to the direction of `a` the field. What is the ratio of their radius of trajectory?

Explanation

To solve the problem of finding the ratio of the radius of trajectory for a proton and a deuteron moving in a uniform magnetic field with equal momenta, we can follow these steps:

### Step 1: Understand the motion of charged particles in a magnetic field
When a charged particle moves in a magnetic field at right angles to the field, it experiences a magnetic force that causes it to move in a circular path. The radius of this circular path can be derived from the relationship between the magnetic force and the centripetal force.

### Step 2: Write the formula for the radius of the trajectory
The radius \( R \) of the circular path for a charged particle in a magnetic field is given by the formula:
\[
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