Practice portal › Dual Nature of Matter and Radiation › Einstein's Photoelectric Equation and Work Function

The photoelectric work function for a metal surface is 4.125 eV. The cut-off wavelength for this surface is:

Asked in AIPMT 1999 · Threshold frequency and wavelength

• (1) 3000 ångström
• (2) 2062.5 ångström
• (3) 4125 ångström
• (4) 6000 ångström

Step-by-step solution

Why the other options are wrong

• (2) 2062.5 is exactly half of 4125, which comes from halving the digits of the work function rather than dividing hc by it
• (3) comes from carries the digits of the work function straight across and calls them ångström
• (4) comes from no single slip reaches 6000 ångström; the check is that a work function near 4 eV always puts the threshold near 3000 ångström, because hc≈12400 eV ångström

Reading this solution needs no sign-in. You only sign in to practise against the clock and keep your progress.