The number of photo-electrons emitted per second from a metal surface increases when:

A point source of light is used in an experiment on photoelectric effects. Which of the following curves best represents the variation of photocurrent \((i)\) with distance \((d)\) of the source from the emitter?

The stopping potential for photoelectrons:

The value of stopping potential in the following diagram is given by:
    

The stopping potential of a photosensitive material is \(4~V\) when the wavelength of incident monochromatic radiation is $$\(\lambda.\) If the wavelength of incident radiation is doubled on the same photosensitive material, the stopping potential becomes \(V.\) The threshold wavelength of the photosensitive material will be:

1.  $\frac{4}{3}\lambda$

2.  $\frac{3}{2}\lambda$

3.  $3\lambda$

4.  $\frac{\lambda }{4}$

The figure shows the variation in photoelectric current \((i)\) with voltage \((V)\) between the electrodes in a photocell for two different radiations. If \(I_a\) and \(I_b\) are the intensities of the incident radiation and \(\nu_a\) and \(\nu_b\) their respective frequencies, then:

The stopping potential as a function of the frequency of the incident radiation is plotted for two different photoelectric surfaces \(A\) and \(B\). The graphs demonstrate that \(A\)'s work function is: