Subject

Physics

Class

CBSE Class 12

Pre Boards

Practice to excel and get familiar with the paper pattern and the type of questions. Check you answers with answer keys provided.

Sample Papers

Download the PDF Sample Papers Free for off line practice and view the Solutions online.
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 Multiple Choice QuestionsShort Answer Type

11.

Name the essential components of a communication system.

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12.

Why does sun appear red at sunrise and sunset?

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13.

Define modulation index. Why is it kept low ? What is the role of a bandpass filter?

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14.

A ray PQ incident normally on the refracting face BA is refracted in the prism BAC made of material of refractive index 1.5. Complete the path of ray through the prism. From which face will the ray emerge ? Justify your answer.

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15.

Calculate the de-Broglie wavelength of the electron orbitting in the n=2 state of hydrogen atom.


Given,

n =2

K.E for the second state, Ek,

 fraction numerator 13.6 over denominator straight n squared end fraction space equals space fraction numerator 13.6 over denominator 4 end fraction
space space space space space space space space space space space equals space 3.4 space x space 1.6 space x space 10 to the power of negative 19 end exponent space J

De-Broglie wavelength, straight lambda space equals space fraction numerator straight h over denominator square root of 2 mE subscript straight k end root end fraction

   equals space fraction numerator 6.63 space straight x space 10 to the power of negative 34 end exponent over denominator square root of 2 space straight x space 9.1 space straight x space 10 to the power of negative 31 end exponent straight x 3.4 straight x 1.6 straight x 10 to the power of negative 19 end exponent end root end fraction

equals space 0.067 space straight m

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16.

Define ionisation energy.

How would the ionisation energy change when electron in hydrogen atom is replaced by a particle of mass 200 times that of the electron but having the same charge ?

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17.

Calculate the shortest wavelength of the spectral lines emitted in Balmer series. [ Given Rydberg constant, R = 107 m-1]

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18.

(i) State law of Malus.

(ii) Draw a graph showing the variation of intensity (I) of polarised light transmitted by an analyser with angle (straight theta) between polarizer and analyser.
(iii) What is the value of refractive index of a medium of polarising angle 60o?

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19.

Sketch the graphs showing variation of stopping potential with frequency of incident radiations for two photosensitive materials A and B having threshold frequencies straight nuA > straight nuB.

(i) In which case is the stopping potential more and why?

(ii) Does the slope of the graph depend on the nature of the material used? Explain.

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20.

a) Write the basic nuclear process involved in the emission of beta plus in a symbolic form, by a radioactive nucleus.

b) In the reactions given below:

i right parenthesis space straight C presubscript 6 presuperscript 11 space rightwards arrow space straight B presubscript straight y presuperscript straight z plus space straight x plus straight nu
ii right parenthesis space straight C presubscript 6 presuperscript 12 space plus straight C presubscript 6 presuperscript 12 space rightwards arrow space Ne presubscript straight a presuperscript 20 space plus space He presubscript straight b presuperscript straight c
Find the values of x, y and z and a, b and c.

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