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What is the work function of the metal if the light of wavelength 4000Å generates photoelectrons of velocity 6 × 10 5 ms –1 from it ? (Mass of electron = 9 × 10 –31 kg; Velocity of light = 3 × 10 8 ms -1 Plank's constant = 6.626 × 10 –34 Js; Charge of electron = 1.6 ×10 –19 JeV –1 )

1. 4.0 eV
2. 0.9 eV
3. 2.1 eV
4. 3.1 eV

Correct answer: 2.1 eV

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