Which year was declared as the international year of Physics?
A. $2002$
B. $2003$
C. $2005$
D. $2007$

Hint: Physics plays an important role in the development of science and technology. It deals with the physical world such as the motion of the body, behavior of matter in space, entities of force, and energy. The main goal of physics is to understand the behavior of the universe. This international year of Physics aimed at raising the awareness of physics and physical sciences.

Complete answer:
The international year of Physics is also known as Einstein year. It was a declaration in recognition of the ${100^{th}}$ anniversary of the ‘Miracle year’ of Albert Einstein. In the ‘Miracle year’, Albert Einstein proposed four landmark papers and the succeeding advances in the field of physics.

The United Nation had declared $2005$ as an international year of physics because in 1905 Albert Einstein proposed the four fundamental fields in physics which are the theory of relativity, quantum theory, the theory of Brownian motion, and the mass-energy relation.
Therefore, option, (C) is the correct option.

Note:In $1905$, Albert Einstein has formulated four landmark papers which are given below:
-In March $1905$, Einstein proposed the wave theory of light in which he said that light is a quanta of particles. This fundamental lead to the development of quantum physics.
-In May $1905$, Einstein formulated the theory of Brownian motion to explain the motion of particles in a fluid. He used the idea of kinetic energy of particles and classical hydrodynamics to derive the equation for the mean free path of particles as a function of time.
-In June $1905$, he formulated the special theory of relativity in which he proved that the absolute time had to be replaced by a new absolute i.e. the speed of light.
In September $1905$, he formulated his most famous equation known as Einstein’s mass-energy relation which is $E = m{c^2}$.