In Rutherford experiment the beam of alpha particles was allowed to fall on a thin foil of gold of thickness 2.1 × 10^–7 m. The scattered alpha-particles were observed through a rotatable detector consisting of zinc sulphide screen and a microscope. The scattered alpha-particles on striking the screen produced brief light flashes or scintillations. These flashes may be viewed through a microscope and the distribution of the number of scattered particles may be studied as a function of angle of scattering. In Rutherford’s nuclear model of the atom, the entire positive charge and most of the mass of the atom are concentrated in the nucleus with the electrons some distance away. The electrons would be moving in orbits about the nucleus just as the planets do around the sun. Rutherford’s experiments suggested the size of the nucleus to be about 10^–15 m to 10^–14 m. From kinetic theory, the size of an atom was known to be 10^–10 m, about 10,000 to 100,000 times larger than the size of the nucleus. Thus, the electrons would seem to be at a distance from the nucleus of about 10,000 to 100,000 times the size of the nucleus itself. Thus, most of an atom is empty space. With the atom being largely empty space, it is easy to see why most α-particles go right through a thin metal foil. However, when α-particle happens to come near a nucleus, the intense electric field there scatters it through a large angle. The atomic electrons, being so light, do not appreciably affect the \(\alpha \)-particles. The scattering data is shown in the following figure.

What is the ratio of the mass of the proton to the mass of the electron (m_p/m_e)?

1836.15

The ratio of m_p/m_e= 1836.15. So, the correct option is (b)