Photoelectric effect, Hertz and Lenard's observations
- Which of the following options represent the variation of photoelectric current with property of light shown on the x-axis?A. Photoelectric current vs Intensity of light: straight line through origin risingB. Photoelectric current vs Intensity of lig… Answer: 1. A only Key idea: at a fixed frequency above the threshold, the photoelectric current is directly proportional to the intensity. A... 1
- The work functions of Caesium (Cs), Potassium (K) and Sodium (Na) are 2.14 eV, 2.30 eV and 2.75 eV respectively. If incident electromagnetic radiation has an incident energy of 2.20 eV, which of these photosensitive surfaces may emit photoelectrons? Answer: 2. Cs only A surface emits photoelectrons only if the photon energy is at least its work function. Cs: 2.20 ≥ 2.14 eV, so it emits.... 1
- Light of frequency 1.5 times the threshold frequency is incident on a photosensitive material. What will be the photoelectric current if the frequency is halved and intensity is doubled ? Answer: 4. zero Photoelectric emission needs frequency ν≥ν₀ , whatever the intensity. Initially ν=1.5ν₀ . Halved, it becomes 0.75ν₀<ν₀ , bel... 1