Class 12th Physics 2017 Set3 Delhi Board Paper Solution
State two important features of Einstein's photoelectric equation.
Einstein's photoelectric equation is:
hv = hv0 + ½ mv2
i.e. Energy of photoelectron (hv) is used in photoelectic current is propotional to the intensity.
Two important features are:
1. Liberating the electron from metal surface is called work function (hv0)
2. Imparting KE to the rejected electrons.
It explains why photoelectric current is proportional to intensity and (v>v0) , however, the emission of electrons are instantaneous. Low intensity of incident radiation does not mean delay in emission.
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A point charge of 2.0 μC is at the centre of a cubic Gaussian surface 9.0 cm on edge. What is the net electric flux through the surface?
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Suppose the spheres A and B in Exercise 1.12 have identical sizes. A third sphere of the same size but uncharged is brought in contact with the first, then brought in contact with the second, and finally removed from both. What is the new force of repulsion between A and B?
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A uniform magnetic field of 1.5 T exists in a cylindrical region of radius10.0 cm, its direction parallel to the axis along east to west. A wire carrying current of 7.0 A in the north to south direction passes through this region. What is the magnitude and direction of the force on the wire if,
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Figure shows a 2.0 V potentiometer used for the determination of internal resistance of a 1.5 V cell. The balance point of the cell in open circuit is 76.3 cm. When a resistor of 9.5 Ω is used in the external circuit of the cell, the balance point shifts to 64.8 cm length of the potentiometer wire. Determine the internal resistance of the cell.
