The wavelength of `K_(alpha)` X-ray for an element is 21.3 pm. It takes 11.3 ke V to knock out an electron from the L-shell of the atom of the element. What should be the minimum accelerating voltage across on X-ray tube having the element as target which allows production of `K_(alpha)` X-ray?

Explanation

To solve the problem, we need to determine the minimum accelerating voltage required in an X-ray tube to produce K-alpha X-rays for an element, given the wavelength of the K-alpha X-ray and the energy required to knock out an electron from the L-shell.

### Step-by-Step Solution:

1. **Convert Wavelength to Meters**:
The wavelength of K-alpha X-ray is given as 21.3 pm (picometers). We convert this to meters:
\[
\text{Wavelength} (\lambda) = 21.3 \text{ pm} = 21.3 \times 10^{-12} \text{ m}
...