Chapter 29, Problem 1RQ

To determine

The predictions that conclude that radioactive emission consists of positively charged particles, negatively charged particles, and neutral particles.

Answer to Problem 1RQ

Solution:

Testing the deflection of radiation in the magnetic field leads to the conclusion that radioactive emission consists of positively charged particles, negatively charged particles, and neutral particles.

Explanation of Solution

Introduction:

Rutherford, in 1899, conducted an experiment in which he set up two parallel metal plates with potential difference between them. Because of the dielectric between them, there was no current in the circuit. Then, he placed a uranium sample between the metal plate gap and observed that there was current in the circuit. This current was due to the ions and free electrons created by the uranium’s radiation. Rutherford covered the uranium sample with a thin aluminum sheet to study how the metal layer affected the amount of radiation. He observed that there was a decrease in the induced current on addition of more sheets to a point after which the current becomes constant. Therefore, he concluded that the radiation consists of at least two components, one of which got absorbed by an aluminum sheet, which consisted of charged particles.

Explanation:

By passing radiation through a magnetic field, the behavior of particles in radiation can be observed.

Rutherford conducted an experiment where the radiation emitting from a radioactive sample passes through a field pointing into the page, and allowed them to fall on a scintillation screen placed perpendicular to the incident beam.

By the right-hand rule, if radiation contains positively charged particles, then the particle should deflect upwards due to the magnetic field. And, if radiation contains negatively charged particles, it should deflect downwards on the scintillation screen.

The outcome was that the scintillation screen glowed in three places: straight ahead, deflected up, and deflected down. And, the downward deflection was much farther than the upward deflection from the un-deflected radiation.

Conclusion:

So, the experiment suggested that the radioactive radiation consists of three components: positively charged particles (alpha particles), negatively charged particles (beta particles), and neutral particles (gamma rays) that were not deflected by the magnetic field.