InterviewSolution
Saved Bookmarks
InterviewSolution
| 1. |
Light of wavelength `lambda_(ph)`falls on a cathode plate inside a vacuum tube as shown in the figure .The work function of the cathode surface is `phi` and the anode is a wire mesh of conducting material kept at distance d from the cathode. A potential different V is maintained between the electrodes. If the minimum de Broglie wavelength of the electrons passing through the anode is `lambda_(e) ` which of the following statement (s) is (are) true? A. For large potential difference `(V gtgt phi//e), lambda_(e)` is approximately halved if V is made four timesB. `lambda_(e)` increases at the same rate as `lambda_(ph)` for `lambda_(ph) lt hc//phi`C. `lambda_(e)` is approximately halved, if d is doubledD. `lambda_(e)` decreases with increase in `phi` and `lambda_(ph)` |
|
Answer» Correct Answer - A `K_("max")= (hc)/lambda_(Ph) - phi` kinetic energy of `e^(-)` reaching the anode will be `K=(hc)/lambda_(Ph)- phi+eV` Now `lambda_(e)=(h)/sqrt(2mK)=(h)/sqrt(2m((hc)/lambda_(Ph)-phi+eV))` If `eV gt gt phi` `lambda_(e)=(h)/sqrt(2m((hc)/lambda_(Ph)+eV))` If `V_(f)=4V_(i)` `(lambda_(e))_(f)=((lambda_(e))_(i))/(2)` |
|