Which of the following event, support the quantum nature of light?

When yellow light is incident on a surface, no electrons are emitted while green light can emit. If red light is incident on the surface, then

Which of the following metal thermionically emits an electron at a relatively lowest temperature among them

Positive rays consists of

In a photoelectric effect experiment, the slope of the graph between the stopping potential and the incident frequency will be

A photosensitive material is illuminated with light of frequency $2.5

u_0$, where$

u_0$ is the threshold frequency. What will be the photoelectric current if the intensity of the incident light is reduced to half while the frequency remains the same?

A parallel beam of light is incident normally on a plane surface absorbing 40% of the light and reflecting the rest. If the incident beam carries 60 W of power, the force exerted by it on the surface is

In cathode ray oscillograph, the focusing of beam on the screen is achieved by

Work function of a metal is $2.1\;eV.$ Which of the waves of the following wavelengths will be able to emit photoelectrons from its surface

Photoelectric effect can be explained by

The {K_α}\;X-ray emission line of tungsten occurs at $\lambda = 0.021nm.$ The energy difference between $K$ and $L$ levels in this atom is about