Question

Splitting of spectral lines under the influence of magnetic field is called:
A.Stark effect
B.Zeeman effect
C.Photoelectric effect
D.Screening effect

Answer 1

Hint: The emission spectrum of an atom is not continuous but rather it is in the form of spectral lines. In the influence of external fields like magnetic or electric fields, these lines separate out from each other.

Complete step by step answer:
The emission spectra of atoms in the gas phase do not show a continuous spread of wavelength but rather they emit light only at specific wavelengths with dark spaces between them. Such spectra are known as line spectra or atomic spectra. In this, emitted radiation is identified by the appearance of bright lines in the spectra. Several lines are named after their discoverers. The splitting of spectral lines of an atom in the presence of magnetic field is known as Zeeman Effect. On the other hand, splitting of spectral lines in the presence of electric fields is known as the Stark effect.

Photoelectric effect is explained as the electrons are ejected from the metal surface when the beam of light strikes on the metal surface. The number of electrons ejected is directly proportional to the intensity of light. For each metal, there is a characteristic minimum frequency below which photoelectric effect is not observed. If a light of energy with frequency higher than threshold frequency falls on the metal surface, the ejected electrons come out with certain kinetic energy. The kinetic energies of these electrons increase with increased frequency of light falling on the surface of metal.

Valence shell electrons suffer force of attraction due to the nucleus and force of repulsion due to the inner shell electrons. The decrease in force of attraction of valence electrons due to the inner electron is called screening effect or shielding effect.

Thus, the correct option is B.

Note:
Photoelectric effect explains the particle nature of light. Whereas phenomena like diffraction explains the wave nature of light. Thus, light has dual nature.