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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 Å is/are:

1. none
2. A only
3. A and B only
4. all three metals

Correct answer: A and B only

Solution

The energy of the incident radiation is calculated using E = hc/λ. For λ = 4100 Å, E ≈ 3.02 eV. Since this energy is greater than the work functions of metals A (1.92 eV) and B (2.0 eV), but less than that of metal C (5 eV), only A and B will emit photoelectrons.

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