Early photoelectric light detectors were based on cesium. Cesium metal has a work function of 3.43 *10^-¹⁹ J. What is the velocity of the photoelectrons ejected from a cesium surface when exposed to blue light at 400 nm? A) 2.90 * 10⁸ m/s B) 2.90 *10⁵ m/s C) 5.81 * 10² m/s D) 5.81 * 10⁸ m/s E) 5.81 *10⁵ m/s

Question

Quizplus · Accepted Answer

The energy of the blue light photon is calculated using E = hc/λ. Subtracting the work function from this energy gives the kinetic energy of the ejected electron, which can be used to find the velocity using KE = 0.5mv².

Early Photoelectric Light Detectors Were Based on Cesium