Question

what can you conclude from the deflection of a cathode ray in a magnetic field? what can you conclude from the deflection of a cathode ray in a magnetic field? the ray must be composed of iron. the ray must have a positive charge. the ray must be composed of charged particles. the ray must need to travel in a vacuum.

Explanation:

When a cathode - ray is deflected in a magnetic field, it indicates the presence of charged particles. Charged particles experience a force in a magnetic field according to the Lorentz force law ($\vec{F} = q\vec{v}\times\vec{B}$), where $q$ is the charge, $\vec{v}$ is the velocity of the particle, and $\vec{B}$ is the magnetic field. It is not necessary for the ray to be composed of iron, and cathode - rays are negatively charged (electrons), not positively charged. Also, while cathode - rays are often studied in a vacuum to avoid collisions with air molecules, the deflection in a magnetic field does not imply that they must travel in a vacuum.

Answer:

The ray must be composed of charged particles.