Question

The wavelength of the K_α line is ______ Pm in copper (Z = 29) if the wavelength of the K_α = line in iron (Z = 26) is known to be equal to 193 picometers.

Options

• 150

• 151

• 152

• 154

Answer 1

The wavelength of the K_α line is 154 Pm in copper (Z = 29) if the wavelength of the K_α = line in iron (Z = 26) is known to be equal to 193 picometers.

Explanation:

By Mosley law `1/lambda ∝ (Z - 1)^2`

`lambda_2/193 = (26 - 1)^2/(29 - 1)^2`

`lambda_2 = (193 xx 25^2)/28^2`

λ₂ = 153.8 pm ≅ 154 pm