Question

When 40 kV is applied across an X-ray tube, X-ray is obtained with a maximum frequency of 9.7 × 1018 Hz. Calculate the value of Planck constant from these data.

Answer 1

The value of Planck constant is 4.12 × 10-15 eVs.

EXPLANATION:

It is given in the question:

• X-ray tube has the applied potential, V = 40 kV

• X-ray’s frequency, $\begin{equation}v=9.7 \times 1018 \mathrm{Hz}\end{equation}$

• Wavelength λ is shown as

• λ=hceV

• where,
• h = Constant of Planck

• c = light’s speed

• $e=1.6 \times 10-19$
• Therefore, λ = hceV ⇒ λc = heV  

• v = cλ ⇒ h = eVv $\Rightarrow h=4.12 \times 10-15 \text { eVs }$