Short Answer 
To find the work function of a photosensitive surface, we use the photon energy of 3.2 eV and the stopping potential of 1.5 V. The maximum kinetic energy of emitted electrons is calculated as 1.5 eV, leading to a work function of 1.7 eV.
Step 1: Understand the Problem
To find the work function of a photosensitive surface, we need to consider the energy of the photons and the stopping potential for the emitted electrons. In this case, the energy of the incoming photons is 3.2 eV and the stopping potential is 1.5 V. This information is crucial to determine the maximum kinetic energy of the emitted electrons.
Step 2: Calculate Maximum Kinetic Energy
The maximum kinetic energy (K.E.) of the emitted electrons can be derived using the relationship between the stopping potential and the kinetic energy. It can be expressed with the formula: K.E. = e * V, where e is the charge of an electron. Hence, we calculate:
- K.E. = 1 * 1.5 eV = 1.5 eV
Step 3: Determine the Work Function
Now, we can find the work function (W) using the formula: W = Photon energy – K.E.. Plugging in the values we have:
- W = 3.2 eV – 1.5 eV
- W = 1.7 eV
This results in a work function of 1.7 eV, confirming that the correct option is (b).