source for studying frequency dependence of photoelectric emission, since it gives a number of spectral lines ranging from the UV to the red end of the visible spectrum. In our experiment with rubidium photo-cell, the following lines from a mercury source were used: # = Å, # = Å, # = Å, # = Å, # = Å, The stopping voltages, respectively, were measured to be: V = . V, V = . V V = .
V, V = . V, V = V Determine the value of Planck’s constant h , the threshold frequency and work function for the material. [ Note: You will notice that to get h from the data, you will need to know e (which you can take to be . × – C).
Experiments of this kind on Na, Li, K, etc. were performed by Millikan, who, using his own value of e (from the oil-drop experiment) confirmed Einstein’s photoelectric equation and at the same time gave an independent estimate of the value of h .] . The work function for the following metals is given: Na: . eV; K: .
eV; Mo: . eV; Ni: . eV. Which of these metals will not give photoelectric emission for a radiation of wavelength Å from a He-Cd laser placed m away from the photocell?
What happens if the laser is brought nearer and placed cm away? . Light of intensity – W m – falls on a sodium photo-cell of surface area cm . Assuming that the top layers of sodium absorb the incident energy, estimate time required for photoelectric emission in the wave-picture of radiation.
The work function for the metal is given to be about eV. What is the implication of your answer? . Crystal diffraction experiments can be performed using X-rays, or electrons accelerated through appropriate voltage.
Which probe has greater energy? (For quantitative comparison, take the wavelength of the probe equal to