Explanation:

Photoelectric emission refers to the emission of electrons from a material when it is exposed to light or other electromagnetic radiation. The maximum kinetic energy of the emitted electrons, denoted as Kmax, is given by the photoelectric equation Kmax = hv - φ0, where h is the Planck's constant, v is the frequency of the incident light, and φ0 is the work function of the material.

I. Kmax is negative:
If Kmax is negative, it would imply that the kinetic energy of the emitted electrons is negative. However, kinetic energy cannot be negative as it is a measure of the energy possessed by a particle due to its motion. Therefore, if Kmax is negative, photoelectric emission would not be possible.

III. Kmax is positive:
If Kmax is positive, it means that the kinetic energy of the emitted electrons is positive. This indicates that the electrons have sufficient energy to overcome the work function of the material and be emitted. Therefore, if Kmax is positive, photoelectric emission is possible.

II. v0 > v:
In the photoelectric equation, v0 refers to the threshold frequency of the material, which is the minimum frequency of light required to cause photoelectric emission. If the frequency of the incident light (v) is less than the threshold frequency (v0), then the kinetic energy of the emitted electrons (Kmax) will be negative. As discussed earlier, negative kinetic energy is not possible, so photoelectric emission will not occur in this case.

In summary, photoelectric emission will not be possible if Kmax is negative or if the frequency of the incident light is less than the threshold frequency. However, if Kmax is positive and the frequency of the incident light is greater than or equal to the threshold frequency, then photoelectric emission is possible.