What did Einstein prove by the photo-electric effect?
1. \(E = h\nu\)
2. \(K.E = \frac{1}{2}mv^2\)
3. \(E= mc^2\)
4. \(E = \frac{-Rhc^2}{n^2}\)

A light of wavelength \(\lambda \) is incident on the metal surface and the ejected fastest electron has speed \(v.\) If the wavelength is changed to \(\frac{3\lambda}{4},\) then the speed of the fastest emitted electron will be:

The work functions for metals \(A,B,\) and \(C\) are respectively \(1.92\) eV, \(2.0\) eV, and \(5\) eV. According to Einstein's equation, the metals that will emit photoelectrons for a radiation of wavelength \(4100~\mathring{A}\) is/are:
1. None
2. \(A\) only
3. \(A\) and \(B\) only
4. All the three metals

According to Einstein's photoelectric equation, the graph between the kinetic energy of photoelectrons ejected and the frequency of incident radiation is:

1.		2.
3.		4.

The current conduction in a discharge tube is due to:
1.  electrons only
2.  +ve ions and –ve ions
3.  –ve ions and electrons
4.  +ve ions and electrons

If a light of amplitude A and wavelength λ is incident on a metallic surface, then the saturation current flow is proportional to (assume cut-off wavelength = ${\lambda }_0$):

1. $A^2,$ $if$ $\lambda$ $>$ ${\lambda }_0$

2. $A^2,$ $if$ $\lambda$ $<$ ${\lambda }_0$

3. $A,$ $if$ $\lambda$ $>$ ${\lambda }_0$

4. $A,$ $if$ $\lambda$ $<$ ${\lambda }_0$