Question

Light of wavelength 180 nm ejects photoelectrons from a metal plate of work function 2 eV. If a magnetic field of 5 × 10⁻³ T is applied parallel to the plate, the radius of the path followed by electrons ejected normally with maximum energy is:

• A. 1.239 m
• B. 0.149 m
• C. 3.182 m
• D. 2.33 m

Hint:

Magnetic field bends electron path into a circle.

Answer 1

The Correct Option is B

Step 1: Photoelectric equation. E = (hc)/(λ) - φ
Step 2: Calculating velocity. K = (1)/(2)mv² v = √((2K)/(m))
Step 3: Radius in magnetic field. r = (mv)/(eB) ≈ 0.149 m