Question

In $\alpha$-ray scattering experiment,

• A. $\alpha$-rays were deviated from their path due to attraction by the electrons
• B. gold foil is used since the number of electrons are more in gold atoms
• C. gold foil is used to prevent the penetration of $\alpha$-particles
• D. $\alpha$-particles are used because they are positively charged and have mass

Answer 1

The correct option is D

$\alpha$-particles are used because they are positively charged and have mass

Explanation for the correct option: (D)

• Rutherford demonstrated that an atom contains the new features of high central charge concentrated into a very small volume in comparison to the rest of the atom, as well as the bulk of the atomic mass of the atom.
• In $\alpha$-ray scattering experiment, alpha particles are positively charged and have mass as they required a strong repelling force to be deflected back.

Explanation for the incorrect options:

A. Rutherford expected the particles to fly straight through the foil. However, he discovered that the particle's path was shifted or deflected when it passed through the foil. It is because, opposite charges repel each other. Thus, the statement given in option (A) is incorrect.

B. In $\alpha$-ray scattering experiment, Rutherford chose gold foil because he wanted the layer to be as thin as possible. This fold foil was approximately 100 atoms thick. Thus, the statement given in option (B) is incorrect.

C. The most malleable metal known to man is gold. It is easily transformed into very thin sheets. The vast majority of alpha particles pass through a piece of metal foil as if it did not exist. Thus, the statement given in option (C) is also incorrect.

Hence, option (D) is correct.