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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 which will emit photoelectrons for a radiation of wavelength 4100 ångström is/are:

Asked in AIPMT 2005 · Work function and the photoelectric equation

• (1) A only
• (2) A and B only
• (3) all the three metals
• (4) none

Step-by-step solution

Why the other options are wrong

• (1) A does emit, but so does B: its work function of 2.0 eV is still below the 3.02 eV the photon carries
• (3) comes from includes C, whose work function of 5 eV is well above the photon energy, so C emits nothing
• (4) comes from says none emit, which would need a photon energy below 1.92 eV; at 4100 ångström the photon carries over 3 eV

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