Define the following in photoelectric effect phenomenon
(a) (i) work function
(ii) Stopping potential (cut-off potential)
(b) calculate energy of photon of wavelenght `3.31 Å`

Explanation

### Step-by-Step Solution

#### (a) Definitions

**(i) Work Function:**
The work function (denoted as \( \phi \)) is defined as the minimum energy required to remove an electron from the surface of a metal. In the context of the photoelectric effect, when light (photons) strikes the metal surface, if the energy of the incoming photons is equal to or greater than the work function, electrons can be emitted from the surface.

**(ii) Stopping Potential:**
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