Physics

ICSE Class 12

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32.
A point source of monochromatic light ‘S’ is kept at the centre C of the bottom of a cylinder. Radius of the circular base of the cylinder is 15.0 cm. The cylinder contains water refractive index = 4/3 to a height of 7.0 cm.

Find the area of water surface through which light emerges in air.

Find the area of water surface through which light emerges in air.

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33.

An astronomical telescope consists of two convex lenses having focal length 80 cm and 4 cm. When it is in normal adjustment, what is its:

(i) Length,

(ii) Magnifying power?

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34.
A convex lens of focal length 5 cm is to be used as a simple microscope. Where should an object be kept so that image formed by the lens lies at least distance D of distinct vision (D = 25 cm)? Also calculate the magnifying power of this instrument in this set up.

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35.
What are characteristic X rays? How are they different from continuous X rays? Give any one difference.

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36.
Wavelength of the 1’st line (H_{α}) of Balmer series of hydrogen is 656.3 nm. Find the wavelength of its 2^{nd} line (H_{β}).

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Graph of [V

This graph is drawn by taking frequency along X-axis and stopping potential along Y-axis as shown in fig.

At starting it is a straight line. The X-intercept gives the threshold frequency v

We can find the slope of graph easily.

The value can also be found from the graph.

In this graph, e = b -a

Therefore, by finding the value of e and slope of graph we can find the Plank’s constant K.

Plank’s constant, K = Slope of graph x e

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38.

(i) Define ‘unified atomic mass unit’.

(ii) Find the minimum energy which a gamma ray photon should possess so that it is capable of producing an electron — positron pair.

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39.
Fission of U - 235 nucleus releases 200 MeV of energy. Calculate the fission rate (i.e. no. of fissions per second) in order to produce a power of 320 MW.

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40.
Draw a neatly labelled circuit diagram of a Full Wave rectifier using two juction diodes.

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