Conditions for photo-electrons emission are:
(i) the energy of the incident photons radiation mus', be greater than the work function of the metal.
(ii) the wavelength of incident radiation must be less than the threshold wavelength for metal surface.
(iii) the frequency of incident radiation must be greater than the threshold, frequency.

(b) Particle characteristics of electroniagnetic waves are:
(i) Thermionic emission
(ii) Photoelectric effect
(iii) Compton effect
(iv) Emission and absorption of incandescence light.
(v) Radiations from heated black bodies.