Question

Which leaves no track on Wilson cloud chamber?
A. Electrons
B. Protons
C. $\alpha $ -particles
D. Neutrons

Answer 1

Hint: Wilson cloud chamber is used to detect the radioactive elements. The radiation or ray which is neutral or uncharged has the highest high penetrating power and is not affected by an electrical and magnetic field and leaves no trace in Wilson cloud chamber.

Complete Step by Step Solution:
In Wilson cloud chamber the radioactive particles are detected by detecting ionising particles.

The alpha particles are actually helium atoms. Helium atoms have a mass number of $4$ and atomic number of $2$ . Thus the alpha particle is a positively charged particle and leaves a trace in the Wilson cloud chamber.

 The electrons are negatively charged species that revolve around the nucleus of an atom. It is highly ionising, leaving no trace in the Wilson cloud chamber.

 The protons are positively charged species that lie in the nucleus of an atom. It is highly ionising, leaving no trace in the Wilson cloud chamber.

Neutron is a subatomic particle of an atom. It is present in the nucleus of an atom. It has no charge and it is not affected by magnetic fields. So, it leaves no track in Wilson cloud chamber
Thus the correct option is D.

Note: Neutron has the highest mass among the other particles of the nucleus. It is an uncharged species and it is not affected by magnetic fields. It is not ionising. It is present in the nucleus of an atom.