﻿ The line AB in the ray diagram represents a lens State whether t

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# 11.The line AB in the ray diagram represents a lens State whether the lens is convex or concave.

We can see that the lens slightly diverges the path of refracted light. Hence, the lens is concave in nature.

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12.

How does one explain, using de Broglie hypothesis, Bohr's second postulate of quantization of orbital angular momentum?

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13.

What is ground wave communication? Explain why this mode cannot be used for long distance communication using high frequencies.

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14.

The equivalent wavelength of a moving electron has the same value as that of a photon of energy 6 x 10–17 J. Calculate the momentum of the electron.

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15.

A ray of light passes through an equilateral glass prism such that the angle of incidence is equal to the angle of emergence and each of these angles is equal to 3/4 of angle of prism. Find the angle of deviation.

OR

Calculate the speed of light in a medium whose critical angle is 45°. Does critical angle for a given pair of media depend on the wavelength of incident light? Give reason.
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16.

Write two important considerations used while fabricating a Zener diode. Explain, with the help of a circuit diagram, the principle and working of a Zener diode as voltage regular.

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17.

Draw the necessary energy band diagrams to distinguish between conductors, semiconductors and insulators.

How does the change in temperature affect the behaviour of these materials? Explain briefly.

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18.

(a) What are the three basic units in communication systems? Write briefly the function of each of these.

(b) Write any three applications of the Internet used in communication systems.
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19.

(a) Write the necessary conditions to obtain sustained interference fringes.

(b) In Young's double slit experiment, plot a graph showing the variation of fringe width versus the distance of the screen from the plane of the slits keeping other parameters same. What information can one obtain from the slope of the curve?

(c) What is the effect on the fringe width if the distance between the slits is reduced keeping other parameters same?

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20.

(a) Give two reasons to explain why reflecting telescopes are preferred over refracting type.

(b) Use mirror equation to show that convex mirror always produces a virtual image independent of the location of the object.
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