Solution:
i. What was the main discovery of Rutherford alpha rays
scattering experiment?
The main discovery of Rutherford alpha rays scattering
experiment was that most of the mass and positive charge of an atom is
concentrated in a very small region called the nucleus, and that most of the
space inside an atom is empty. He also discovered that the electrons are
orbiting around the nucleus at a large distance. He based his discovery on the
observation that most of the alpha particles passed through a thin gold foil
without any deflection, some were deflected by small angles, and very few were
deflected by nearly 180 degrees.
ii. What is the condition for the origin of spectra?
The condition for the origin of spectra is that an atom or a
molecule must undergo a transition from one energy level to another, either by
absorbing or emitting a photon of a specific frequency. The frequency of the
photon is equal to the difference between the energies of the two levels
divided by Planck's constant. The spectrum is a graphical representation of the
intensity of light emitted or absorbed at different frequencies.
iii. Name the series of spectra and different colors which
belong to visible range.
The series of spectra that belong to visible range are
called Balmer series, which correspond to the transitions of electrons from
higher energy levels to the second energy level (n=2) in hydrogen or
hydrogen-like atoms. The different colors that belong to visible range are red,
orange, yellow, green, blue, indigo and violet. The Balmer series consists of
four spectral lines in visible range: H-alpha (red), H-beta (blue-green),
H-gamma (blue) and H-delta (violet).