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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?

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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)

Given _aμ^w = 3/2 and _aμ^w = 4/3

The normal position of the fish due to water is,

$straight d subscript 1 space equals space straight t subscript 1 space open parentheses 1 minus 1 over straight a subscript 2 straight w end subscript close parentheses space space space space space equals space 10 space open parentheses fraction numerator 1 over denominator 4 divided by 3 end fraction close parentheses space space space space space equals space 10 open parentheses 1 minus 3 over 4 close parentheses space space space space equals space 10 over 4 space equals space 2.5 space cm Normal space shift space of space fish space due space to space glass space is comma space straight d subscript 2 space equals space straight t subscript 2 open parentheses 1 minus 1 over straight a subscript straight g close parentheses space space space space space space equals space straight t subscript 2 open parentheses 1 minus fraction numerator 1 over denominator 3 divided by 2 end fraction close parentheses space space space space space equals space 2 space open parentheses 1 space minus space 2 over 3 close parentheses space space space space equals space 2 over 3 space equals space 2 over 3 space cm We space have space distance comma space straight d space equals space straight t subscript 1 space open parentheses 1 minus 1 half close parentheses space semicolon space where comma space straight t space is space thickness Now comma space Apparent space distance space of space fish comma space equals space space straight d subscript 1 space plus space straight d subscript 2 equals space straight t subscript 1 space open parentheses 1 minus 1 over straight alpha subscript 1 close parentheses space plus space straight t subscript 2 space open parentheses 1 minus 1 over straight alpha subscript 2 close parentheses space space space space space space space space space space space space space space space space space space space open square brackets because space straight d space equals space straight t open parentheses 1 minus 1 over straight alpha close parentheses close square brackets space equals space 10 open parentheses 1 minus space fraction numerator 1 over denominator 4 divided by 3 end fraction close parentheses space plus space 2 space open parentheses 1 minus fraction numerator 1 over denominator 3 divided by 2 end fraction close parentheses equals space 10 space open parentheses 1 minus 3 over 4 close parentheses space plus space 2 space open parentheses 1 minus 2 over 3 close parentheses equals space 10 open parentheses fraction numerator 4 minus 3 over denominator 4 end fraction close parentheses space plus space 2 space open parentheses fraction numerator 3 minus 2 over denominator 3 end fraction close parentheses equals space 10 space straight x space 1 fourth space straight x 2 space straight x space 1 third equals space 5 over 2 space plus space 2 over 3 space equals space fraction numerator 15 plus 4 over denominator 6 end fraction space equals space 19 over 6 space equals space 3.17 space cm$

Therefore, the apparent position of the fish is 3.17 cm.