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ISC Class 12 Physics Solved Question Paper 2004

Short Answer Type

21. An ionized helium particle (+2e) is situated at the origin (0, 0). How much work is done in taking an electron from x = 3 cm to x = 6 cm?

Here,

$Work space done comma space straight U space equals space fraction numerator 1 over denominator 4 πε subscript straight o end fraction space fraction numerator straight q subscript 1 straight q subscript 2 over denominator straight r squared end fraction straight U subscript 1 space space equals space fraction numerator negative 1 over denominator 4 πε subscript straight o end fraction. space fraction numerator 2 straight e squared over denominator 3 end fraction straight U subscript 2 space equals space fraction numerator negative 1 over denominator 4 πε subscript straight o end fraction. space fraction numerator 2 straight e squared over denominator 6 end fraction straight U space equals space straight U subscript 2 space minus space straight U subscript 1 space space space space equals space fraction numerator 2 straight e squared over denominator 4 πε subscript straight o end fraction open parentheses 1 over 6 space minus space 1 third close parentheses space space space space equals space minus space fraction numerator 2 straight e squared over denominator 4 πε subscript straight o end fraction open parentheses fraction numerator 1 minus 2 over denominator 6 end fraction close parentheses space space space equals space minus space fraction numerator 2 straight e squared over denominator 4 πε subscript straight o end fraction open parentheses fraction numerator negative 1 over denominator 6 end fraction close parentheses space space space equals space fraction numerator 9 space straight x space 10 to the power of 9 space straight x space 2 space straight x space left parenthesis 1.6 space straight x space 10 to the power of negative 19 end exponent right parenthesis squared over denominator 6 end fraction space space space space equals space 7.68 space straight x space 10 to the power of negative 29 end exponent space straight J$

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22. Given that the resistance of the voltmeter is 400 Ω, find the voltmeter’s reading.

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23. Show that the radius of a charged particle entering perpendicularly in a magnetic field is directly proportional to its momentum.

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24. Find the inductance of a choke coil needed to run an arc lamp, with an a.c. source of 100 V supply at 50 Hz. The arc runs at 10 amp. current and has an effective resistance of 4 Ω.

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25. State any five electromagnetic waves and arrange them in the increasing order of their penetrating power.

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26.

What type of wave front is produced by:

(i) Point source of light (ii) Line source of light

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27. Define dispersive power. The dispersive power of an achromatic doublet is 2/3 and the combined focal length of the combination is 30 cm. Find the focal length of each lens stating its nature.

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28.

Calculate the focal length of a concave lens with the help of the above ray diagram. Focal length of convex lens is 20 cm.

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29.

A fish is located at a distance of 10 cm from the wall of a fish pond. The thickness of the glass wall is 2 cm. Find the apparent position of the fish. (Given

_aμ_g = 3/2 and _aμ_w= 4/3)

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