Define each of the following with respect to semiconductors:

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 (I) Hole : It is the vacant space that occur due to absence of an electron in an atom.

(II) Forbidden gap : It is the gap getween the valence band and conduction band.

(III) Donor atoms : They are pentavalent impurity atoms which adds electrons to form N-type semiconductor.

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An electrostatic CRT has parallel deflection plates 1.5 cm long and 6mm apart. The screen is 55cm from the centre of the deflecting plates. The deflecting and accelerating potentials are 150 V and 2.5 kilovolts respectively. Determine the:

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