Question

The source of energy of the sun is ---.
(A)Chemical reaction
(B)Nuclear fusion
(C)Photoelectric effect
(D)Nuclear fission

Answer 1

Hint: Energy in the form of light is obtained only when there is something happening which can give enormous amounts of heat energy. The elements helium and hydrogen are responsible for this enormous energy in the sun.

Complete answer:
The specific type of reaction occurring inside the core of the sun is proton-proton fusion reaction. The energy in the form of heat and light from the sun is due to this nuclear fusion which is responsible for the shining of the star. The reaction actually happening is between protons, protons of a hydrogen atom (protium isotope or just hydrogen nucleus). Its nucleus consists of a single proton which combines with another hydrogen nucleus or proton –this is called nuclear fusion.
Steps involved in nuclear fusion of sun-
1)Two protons fuse together or join together and then split up and transform to form a neutron and proton pair. The neutron resulting from the weak nuclear force forms two other particles with it called positron and neutrino, the proton-neutron forms deuterium (an isotope of hydrogen).
2)The deuterium collides with another proton and transforms to a given helium (He-3) nucleus and gamma ray. These gamma rays are the major light radiation of the sunlight.
3)The He-3nucleus combines with another helium 3 nucleus to form the He-4 nucleus (source of helium in sun).

Note:
The nuclear fusion equation in the sun is $H + H \to D + {\beta ^ + } + \nu $. Where H is proton, D is deuterium,${\beta ^ + }$ represents a positron or beta particle,$\nu $ represents neutrino.