Question

The threshold wavelength of tungsten is \(2300\,\text{\AA}\). If ultraviolet light of wavelength \(1800\,\text{\AA}\) is incident on it, then the maximum kinetic energy of photoelectrons would be about:

• A. \(1.49\,\text{eV}\)
• B. \(2.2\,\text{eV}\)
• C. \(3.0\,\text{eV}\)
• D. \(5.0\,\text{eV}\)

Hint:

Use wavelengths in directly with \(hc=12400\,\text{eV\AA}\).

Answer 1

The Correct Option is A

Step 1: \[ K_{\max}=hc\left(\frac{1}{\lambda}-\frac{1}{\lambda_0}\right) \]
Step 2: \[ K_{\max}=12400\left(\frac{1}{1800}-\frac{1}{2300}\right)\text{ eV} \] \[ K_{\max}\approx1.49\,\text{eV} \]