A charged particle is moving in a circular orbit with radius $r$ and orbital angular frequency $\omega$ in the presence of a magnetic field. The orbit is enclosed within a larger circular metallic frame. The frame is concentric and coplanar with the orbit. The radius of the frame is now gradually decreased. Assuming that the particle remains within the frame at all times, what changes to the trajectory of the particle will occur as the frame is being shrunk?

• Correct answer
  A

  The radius of the orbit will gradually decrease and the frequency will gradually increase.
• B

  The radius of the orbit will gradually increase and the frequency will gradually decrease.
• C

  The radius of the orbit will remain the same but the frequency will gradually increase.
• D

  Both the radius of the orbit and the frequency will remain unchanged.

Hence, the correct answer is option: 'A'.