Chapter 32, Problem 1RCQ

To determine

The reason the alpha particles fired through a piece of gold foil emerge undeflected.

Answer to Problem 1RCQ

Solution:

Most alpha particles emerging from a gold foil are undeflected, because the alpha particle pass through the empty space in the atom. And some are repelled because more massive cores of atoms of the same kind.

Explanation of Solution

Most of the atoms have empty space inside them. The radius of an atom is about 100000 times greater than the radius of its nucleus. So, nucleus occupies a very small volume of the atom. Alpha particles are deflected only by the nucleus. This deflection is due to the electromagnetic force between the proton of the nucleus and those of the alpha particle.

Hence, most of the time the alpha particle would pass through the empty space in the atom and not be deflected.

Conclusion:

Thus, the alpha particles emerging from a gold foil are undeflected.