Question

A beam of electrons has an energy of 1 joule. How many electrons are in the beam?

[1 eV = 1.6 × 10⁻¹⁹ J]

Answer 1

The energy of one electron is 1.6 × 10⁻¹⁹ J.

\[ \text{Number of electrons} = \frac{\text{Total energy}}{\text{Energy of one electron}} \]

\[= \frac{1}{1.6 \times 10^{-19}} \]

= 6.25 × 10¹⁸

So, the beam contains 6.25 × 10¹⁸ electrons.