Question

Which of the following items was not discovered using the cathode ray tube?

1) X-rays
2) Electrons
3) Protons
4) Neutrons

Answer 1

Protons were not discovered using the cathode ray tube. This device helped in the discovery of electrons and X-rays, but the neutron was found by noting its absence.

Step-by-step explanation:

The item that was not discovered using the cathode ray tube is 3) Protons.

The cathode ray tube experiments helped in the discovery of the electron by showing the presence of negatively charged electrons emitted by the cathode. It also aided in the discovery of X-rays, as German physicist Wilhelm Roentgen used a cathode ray tube to discover X-rays in 1895.

However, the neutron was initially found not by a direct observation, but by noting what was not found. The presence of protons and electrons was already known, and the absence of any other particle led to the discovery of the neutron later on.