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ISC Class 12 Physics Solved Question Paper 2011

Short Answer Type

41. Starting with the law of radioactive disintegration, show that : N = N₀e^{-λ t,} where the terms have their usual meaning.

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42. What is meant by Pair Production ? Explain with the help of an example and a balanced equation.

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43.

An X ray tube is operated at a tube potential of 40,000 V. Calculate :

(i) Kinetic energy of an electron emitted by the filament when it reaches the target / anode.

(ii) Wavelengths of all the X rays emitted by the X ray tube.

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44. (i)In the following nuclear reaction, calculate the energy released in MeV :

straight H presubscript 1 presuperscript 2 space plus space straight H presubscript 1 presuperscript 2 space rightwards arrow space He presubscript 2 presuperscript 3 space plus space straight n presubscript 0 presuperscript 1

Given that: Mass of

straight H presubscript 1 presuperscript 2

= 2.015 u
Mass of

He presubscript 2 presuperscript 3 space equals space 3.017 space straight u

Mass of on = 1.009u

(ii) What is the name of this reaction ?

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45.

What is meant by the terms :

(i) a full wave rectifier ?

(ii) an amplifier ?

(iii) an oscillator ?

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46. Using several NAND gates, how can you obtain an AND gate ? Draw a labelled diagram in support of your answer.

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Long Answer Type

47. Obtain an expresssion for intensity of electric field in end on position. i.e., axial position of an electric dipole.

Let an electric dipole is taken which constitutes (+q) and (- q) charge separated by the distance 2l.

Let from the mid point of the dipole at a distance ‘r’ is the point P at intensities due to (+q) and (-q) charge respectively.

$straight E subscript 1 space equals space fraction numerator 1 over denominator 4 πε subscript straight o end fraction fraction numerator straight q over denominator left parenthesis straight r space minus space straight l right parenthesis squared end fraction space semicolon space$ direction along the dipole axis.

E₂ = $fraction numerator 1 over denominator 4 πε subscript straight o end fraction space fraction numerator q over denominator left parenthesis r plus l right parenthesis squared end fraction semicolon$ direction opposite to the dipole axis.

Resultant electric field intensity E = E₁ - E₂

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