i) Define half-life of a radioactive substance.ii) Using the equ

Subject

Physics

Class

ICSE Class 12

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 Multiple Choice QuestionsShort Answer Type

41.

Find the minimum wavelength of the emitted X-rays, when an X-ray tube is operated at 50 kV.

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42.

i) Define half-life of a radioactive substance.

ii) Using the equation, N = No e-straight lambdat, obtain the relation between half-life (T) and decay constant (straight lambda right parenthesis of a radioactive substance.


i) The time-interval in which the mass of a radioactive substance, or the number of its atoms, is reduced to half its initial value is called the 'half-life' of that substance.

ii) Let No be the number of atoms present in a radioactive substance at time t =0

N be the number at a later time t.


space space space space space space straight N subscript straight o over 2 equals space N subscript o space e to the power of negative lambda t end exponent
rightwards double arrow space space space 1 half space equals space e to the power of negative lambda t end exponent
italic rightwards double arrow italic space italic space space e to the power of lambda t end exponent italic space italic equals italic space italic 2
italic rightwards double arrow italic space italic space italic space italic space italic space italic space lambda t italic space italic equals italic space italic log subscript e italic 2
i italic. e italic. italic comma italic space T italic space italic equals italic space fraction numerator italic log subscript e italic 2 over denominator lambda end fraction italic space
italic space italic space italic space italic space italic space italic space italic space italic space italic space italic space italic space italic space italic equals italic space fraction numerator italic 0 italic. italic 6931 over denominator lambda end fraction

This is the relation between half-life and decay constant.

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43.

With the help of a suitable example and an equation, explain the term pair production.

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44.

Draw a labelled diagram of a full wave rectifier. Show how output voltage varies with time, if input voltage is a sinusoidal voltage.

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45.

What is a NAND gate? Write it's truth table?

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 Multiple Choice QuestionsLong Answer Type

46.

Derive an expression for intensity of electric field at a point in broadside position or on an equatorial line of an electric dipole.

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47.

Figure below shows a capacitor C, an inductor L and resistor R, connected in series to an ac supply of 220 V.


Calculate:

i) the resonant frequency of the given LCR circuit

ii) current flowing through the circuit

iii) Average power consumed by the circuit.

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48.

On the basis of Huygen's wave theory of light, show that the angle of reflection is equal to the angle of incidence. You must draw a labelled diagram for this deviation.

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