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The work function of metals is in the ra...

The work function of metals is in the range of 2 eV to 5 eV. Find which of the following wavelength of light cannot be used for photoelectric effect. (Consider, Planck's constant `= 4 xx 10^(-15) eV.s`, velocity of light `= 3 xx 10^(8) m//s`)

A

510 nm

B

650 nm

C

400 nm

D

570 nm

Text Solution

Verified by Experts

The correct Answer is:
B
The energy of the incident photons should not be less than 2eV.
Energy of the photon, `E = hv = (hc)/(lamda)`,
Hence, maximum value of the wavelength,
`lamda_(m) = (hc)/(E) = ((4 xx 10^(-15)) xx (3 xx 10^(8)))/(2) = 6 xx 10^(-7) m`
`= 600 xx 10^(-9) m = 600 nm`
Therefore, light of wavelength 650 nm cannot be used for photoelectric effect.
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