Question

As soon as physicists began to discover that there might be something smaller than the atom, the best diagnostic tool to investigate these mysterious entities was the use of a magnetic field. Most subatomic particles have a charge, and are therefore deflected in magnetic and electric fields. Particle physicists have used a multitude of apparatuses to determine the nature of the various subatomic particles. For decades, the cloud chamber allowed physicists to see the vapour trails of particles flying through the condensed alcohol clouds of the chamber. If they applied magnetic and electric fields to regions of the cloud chamber, they could analyze charge and mass properties from the observed deflections. The cloud chamber was succeeded by the bubble chamber. The bubble chamber is similar to the cloud chamber. Particles are still not observed directly, but evidence of their passage is. Bubbles form in the liquid used in the bubble chamber whenever ionizing particles or radiation are present, creating tracks. These tracks can be manipulated if magnetic and electric fields are applied to the chamber. B into the page nucleus Y gamma ray Z Z 6. Using the information presented above: • Identify the two individual particles, Y and Z. Justify your response. Explain the spiral nature of the deflection of the particles.

Answer 1

The Y and Z particles appear to be position and electron pair.

Reason: one of them is spiralling clock wise and other is spiralling anti clockwise thus indicating that they have opposite charge - since the centripietal force qVXB is +eV x B for positron and is -eV x B for electron.

It can be noted that for both these particles magnitude of force is same, their masses and velocities are same.

Hence radius of circular orbit ,r

mv^2/r = qvB , if V and B are perpendicular to each other

r = mv/qB, thus r is same for both particles in magnitude.

But electron has clock wise rotation ,if B is into page and vice versa for positron.

The spiralling path is result of loss of energy of the particles due to collision with bubble atoms and consequent reduction in velocity of particles.