Answer:
The initially known quantity, together with the wavelength, that is sufficient to calculate the stopping potential for electrons from the surface of a metal is called the WORK FUNCTION.
Explanation:
The stopping potential is defined as the potential that is required to stop electrons from being ejected from the surface of a metal when light with energy greater than the metal's work function/work potential is incident on the metal.
Given that light is known to be made up of photons, which carry energy in packets according to the frequencies of the light.
The photoelectric phenomenon explains that when light of a certain frequency that corresponds to an energy level that is higher than a metal's work function is incident on a metal, it will lead to electrons being ejected from the surface of the metal. The energy of the ejected electrons is then proportional to the difference between the energy level of the photons and the metal's work function.
Basically, it is the excess energy after overcoming the work function that rejects the electrons.
So, to prevent this excess energy from ejecting electrons from a metal's surface, an energy thay matches this excess must be in place to stop electrons from coming out. This energy/potential required to stop the ejection of electrons, is called the stopping potential.
The stopping potential is given as
eV₀ = hf - ϕ
The stopping potential (eV₀) them depends on the hf and the ϕ.
hf is the energy of the photons, where h is Planck's constant and f is the photons' frequency which is further given as
f = (c/λ)
c = speed of light (speed of the photons)
λ = wavelength of the photons.
The other quantity, ϕ, is the metal's work function; the amount of energy needed to be overcome by the photons before ejection of electrons is possible. It is the minimum energy that the light photoms must possess to even stand a chance of being able to eject electrons from a metal's surface.
So, the stopping potential is the difference between the energy of the photons (obtained using the photons' frequency, wavelength and/or speed) and the metal's work function.
Hope this Helps!!!!
and 
, we find the intensity of the sound wave: