In a photoelectric effect experiment,light of frequency $1.5$ times the threshold frequency is made to fall on the surface of a photosensitive material. If the frequency is halved and the intensity is doubled,the number of photoelectrons emitted will be:

Define threshold frequency.

Choose the correct option for the given statements:
Statement-$I$: The kinetic energy of photoelectrons emitted by a photosensitive surface depends on the intensity of the incident radiation.
Statement-$II$: In the photoelectric emission process,the maximum kinetic energy of the photoelectrons increases with increasing intensity of the incident light.

The graph between the intensity of light $(I)$ falling on a metallic plate and the generated photoelectric current $(i)$ is:

What is the intensity of radiation (light)?

Write the characteristics of the photoelectric effect.