Question

When 0.50AA X-rays strike a material, photoelectrons from the K shell are observed to move in a circle of radius 23mm in a magnetic field of 2×10⁻2T acting perpendicular to the direction of emission. What is the binding energy of K-shell electrons?

• A. \(3.5\,\text{keV}\)
• B. \(6.2\,\text{keV}\)
• C. \(2.9\,\text{keV}\)
• D. 5.5keV

Hint:

In photoelectric problems: • Use magnetic field motion to find kinetic energy. • Binding energy = photon energy – kinetic energy.

Answer 1

The Correct Option is B

Step 1: Photon energy: E = (hc)/(λ) = (12400)/(0.5) = 24.8keV
Step 2: Velocity of photoelectron from magnetic motion: v = (qBr)/(m)
Step 3: Kinetic energy: K = (1)/(2)mv² ≈ 18.6keV
Step 4: Binding energy: Eb = 24.8 - 18.6 = 6.2keV