Download Physics for You 11 2016 PDF

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Page 2

PHYSICS FOR YOU | NOVEMBER ‘16 7

Class 11

NEET | JEE Essentials 8

Ace Your Way CBSE 21

JEE Workouts 31

MPP-5 35

Brain Map 46

Class 12

NEET | JEE Essentials 40

Brain Map 47

Ace Your Way CBSE 59

JEE Workouts 67

Exam Prep 71

MPP-5 76

Competition Edge

Physics Musing Problem Set 40 80

You Ask, We Answer 81

Physics Musing Solution Set 39 83

Crossword 85

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Mahabir Singh

Editor
Anil Ahlawat
(BE, MBA)

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Volume 24 No. 11 November 2016

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PHYSICS FOR YOU | NOVEMBER ‘16 45


μ μ μ μ2 1 2 1
v u R
− =



Lense s
A • lens is a transparent medium bounded by two
refracting surfaces such that at least one of the
refracting surfaces is curved.
If the thickness of the lens is negligibly small in •
comparison to the object distance or the image
distance, the lens is called thin.
Broadly, lenses are of the following types : •

�e focal length ( • f ) of a lens depends upon the
refractive indices of the material of the lens and the
medium in which the lens is present and the radii
of curvature of both sides. �e following relation
giving focal length (f ) is called as lens maker�s
formula.


1

1
1 1

0 1 2f R R
= −

⎝⎜


⎠⎟












μ
μ

where μ = refractive index of the material of the lens,
μ0 = refractive index of the medium.

Lens formula •


1 1 1
v u f
− =

� • e ratio of the size of the image formed by a lens to
the size of the object is called linear magni�cation
produced by the lens. It is denoted by m.

If h1 and h2 are the sizes of the object and image
respectively, then

m
h
h

v
u

= =2
1

.

� • e power of a lens is de�ned as the reciprocal of
the focal length in metre.

P
f

=
1

( )in m
�e SI unit of power of lens is diopter (D).
For a convex lens, P is positive.
For a concave lens, P is negative.
When focal length ( f) of lens is in cm, then

P
f

=
100

( )
.

in cm
dioptre

When a number of thin lenses of focal length • f1, f2,
... etc. are placed in contact coaxially, the equivalent
focal length F of the combination is given by


1 1 1 1

1 2 3F f f f
= + + + ....

�e tot al power of the combination is given by
P = P1 + P2 + P3 + ...

�e total magni�cation of the combination is
given by

m = m1 × m2 × m3 ....
When two thin lenses of focal lengths • f1 and f2 are
placed coaxially and separated by a distance d, the
focal length of combination is given by


1 1 1

1 2 1 2F f f
d

f f
= + − .

In te rms of power, P = P1 + P2 � dP1P2.
Silvering of a lens : • Let a planoconvex lens is having
a curved surface of radius of curvature R and has
refractive index μ.

If its plane surface is silvered, it behaves as a
concave mirror of focal length

f
R

= −
−2 1( )μ

If the curved surface of planoconvex lens is
silvered then it behaves as a concave mirror of
focal length

f
R

= −


Displacement method is used to determine focal •
length of convex lens in laboratory.

Page 79

PHYSICS FOR YOU | NOVEMBER ‘16 85

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ACROSS
2. The dissociation of molecules by nuclear radiation.

[10]
3. The adiabatic rate at which temperature falls with

increasing altitude. [5, 4]
4. The electromagnetic wave produced by klystron

valve. [9]
5. The moon of mars that has orbital period of 7.66

hours. [6]
7. An instrument used for measuring the total pressure

of fluid stream. [5, 4]
10. A prefix denoting 1021. [5]
11. An instrument uses polarised light for studying the

properties of substances. [11]
15. The temperature at which the two forms of liquid

helium can exist together. [6, 5]
16. A simple pendulum that demonstrates the earth’s

rotation. [8, 8]
21. A unit of loudness of sound. [4]
23. The rectangular pattern of image capture and

reconstruction in television. [6, 4]
25. A measure of amount of magnetic flux embraced by

an electric circuit. [7]
13. The god particle. [5, 5]
14. The process of changing the waveform of transmitted pulses.

[5, 7]
17. The condition in which people or objects appear to be

weightless. [12]
18. The branch of physics concerned with properties of sound.

[9]
19. A device used to measure the thickness of the eye’s cornea.

[10]
20. A common boundary between two parts, devices or systems.

[9]
22. The solid carbon dioxide, used as a refrigerant. [3, 3]
24. An instrument for measuring rate at which water evaporates.

[9]
26. The maximum number of digital inputs that a single logic

gate can accept. [3, 2]



27. A hypothetical elementary particle responsible for the effects
of gravitation. [8]

28. An imaginary line connecting places of equal barometric
pressure. [6]

29. A high-voltage electric short circuit made through the air
between exposed conductors. [9]

DOWN
1. The condition at which entropy of an isolated system is

maximum. [4, 5]
2. A temperature scale in which ice point is taken as 0° and the

steam point as 80°. [7, 5]
6. A single input-output device which has a gain of one. [6]
8. A resistor inserted into a circuit to compensate for changes

arising from temperature fluctuations. [9]
9. High-frequency static disturbance of cosmic origin. [6,5]
12. An effect occurring in transmission lines when the load is

suddenly reduced to very small value. [8, 6]

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86 PHYSICS FOR YOU | NOVEMBER ‘16

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