Question

1 MeV is equal to:
A. \[1.6\times {{10}^{-19}}J\]
B. \[1.6\times {{10}^{-14}}J\]
C. \[1.6\times {{10}^{-13}}J\]
D. \[1.6\times {{10}^{13}}J\]

Answer 1

Hint: Electron volt is the amount of work required to move an electron across a potential difference of 1 volt. To get 1 MeV we have to multiply the electron volt value with \[{{10}^{6}}\].

Complete step by step answer:
Electron volt \[(eV)\] is a unit of energy, which is equal to the work done on an electron to move across a potential difference of 1 volt.
\[1eV=1.602\times {{10}^{-19}}\text{joules}\]
Therefore,
\[1MeV=1.602\times {{10}^{-19}}\text{joules}\times {{10}^{6}}\]
\[1MeV=1.602\times {{10}^{-13}}\text{joules}\]
So, the correct option is C.

Additional information:
Electron volt is advised to use in electrostatics since the charge can be quoted in integer units of elementary charge.
Alternatively, we can define electron volt as the kinetic energy acquired by an electron when it is accelerated through a potential difference of one volt. Since the charge on an electron is negative, it requires work to shift an electron from a high potential to a lower potential.
The electric potential at a point in an electric field is defined as the work done in bringing a unit positive charge from infinity to the point. It is a scalar quantity. The potential at infinity will be zero.
Change in electric potential energy will be equal to the negative work done by the electric field. If an electric field does a positive work then electric potential will be negative. If an electric field does a negative work then electric potential energy will be positive. The electric potential energy of a charged particle in an electric field depends not only on the electric field but also the charge of the particle.
We can write the equation of electric potential as,
\[V=\dfrac{U}{q}\], where \[V\] is the electric potential and \[U\] is defined as electric potential energy.
The electric potential has a value everywhere in space but has no direction.

Note: Students are advised to multiply the electron volt with \[{{10}^{6}}\] to get \[1MeV\]. The options will confuse candidates, because \[1.602\times {{10}^{-19}}\text{joules}\] is also there. It is actually 1 eV It is one million times of electron volt.