If light of wavelength 412.5 nm is incident on each of the the metals given below, which ones will show photoelectric emission and why?
Metal | Work Function |
Na | 1.92 |
K | 2.15 |
Ca | 3.20 |
Mo | 4.17 |
A metal will show photoelectric emission in below situation:
E ≥ work funciton
Now according to the relation below:
E = h (c/λ)
E = 1240 / λ
λ = 1240 /412.5 nm
λ = 3.006 eV
So here, work function of k and Na are less than incident energy of photon. Hence, only potassium (k) and Sodium (Na) will show photoelectic emission.
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(a) Estimate the number of electrons transferred (from which to which?)
(b) Is there a transfer of mass from wool to polythene?
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A conducting sphere of radius 10 cm has an unknown charge. If the electric field 20 cm from the centre of the sphere is 1.5 × 103 N/C and points radially inward, what is the net charge on the sphere?
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(a) Base, emitter and collector regions should have similar size and doping concentrations.
(b) The base region must be very thin and lightly doped.
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(d) Both the emitter junction as well as the collector junction are forward biased.
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(a) A vector needs three quantities for its specification. Name the three independent quantities conventionally used to specify the earth's magnetic field.
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Would you expect a greater or smaller dip angle in Britain?
(c) If you made a map of magnetic field lines at Melbourne in Australia, would the lines seem to go into the ground or come out of the ground?
(d) In which direction would a compass free to move in the vertical plane point to, if located right on the geomagnetic north or south pole?
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