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TitlePhysics XII
TagsElectrical Resistance And Conductance Electric Current Capacitor Electrical Resistivity And Conductivity Dielectric
File Size1.9 MB
Total Pages168
Document Text Contents
Page 1

1 XII – Physics

Sl. No. Name Designation

1. Sh. V.K. Gaur Principal
R.P.V.V., Shankaracharya Marg,
Delhi-110054

2. Sh. Pundrikaksh Kaudinya Vice Principal
R.P.V.V., Rajniwas Marg,
Delhi-110054

3. Ms. Girija Shankar PGT (Physics)
R.P.V.V., Surajmal Vihar
Delhi-110092

4. Mr. Kulbir Singh Antil PGT (Physics)
R.P.V.V., Kishan Ganj,
Delhi-110007

5. Mr. Devendra Kumar PGT (Physics)
R.P.V.V., Yamuna Vihar,
Delhi-110053

6. Ms. Madhu Gupta PGT (Physics)
R.P.V.V., Lajpat Nagar
Delhi-110024

Page 2

2

1. Electrostatics 3

2. Current Electricity 20

3. Magnetic Effects of Current and Magnetism 41

4. Electromagnetic Induction and Alternating Currents 59

5. Electromagnetic Waves 77

6. Optics 82

7. Dual Nature of Matter and Radiation 98

8. Atoms and Nuclei 104

9. Electronic Devices 116

10. Communication Systems 130

Sample Papers 137

Page 84

84

Astronomical Telescope
Magnification

(a) When image is formed at infinity
0

e

f
m

f

(b) When image is formed at D
0 01
e

f fm
f D

Length of tube L = fo + fe

Angular limit of resolution
1.22

D

The resolving power
1

1.22
D

Reflection Telescope

Magnifying power
0

e

f
m

f

Brightness
2

2
D

B
d

Wave Optics
Young’s Double Slit Experiment

Intensity of light 2 21 2 1 2I 2 cosa a a a

Constructive Interference
Phase difference = 2n

Path difference x = n

Destructive Interference
Phase difference = (2n + 1)

Path difference x = (2n + 1) /2

Ratio of light intensity at maxima and minima

2
1 2max

2
min 1 2

a aI
I a a

Path difference
yd

x
D

Fringe width (For Dark and Bright Fringes) = yn – yn–1 = D/d

The angular width of each fringe
D d

Single Slit Diffraction

Central maximum 1 1sin ;a
up to which central

maximum extends on both sides from centre.

Angular width = 2 1
For nth secondary minima sin n = n /a

Page 85

85

For nth secondary maxima
2 1sin ´

2n
n

a

Fringe width (For Dark and Bright Fringes) 1 1´ ´n n n n
D

y y y y
a

Fresnel distance
2

FZ
a

Brewster’s Law r + p = 90°

Law of Malus I = I0 cos
2

If two coherent beams have different intensities I and 0max 1 2 1 2I I I 2 I I cos 0

I2, the resulting minima and maxima will be
2

1 2I I

min 1 2 1 2I I I 2 I I cos 180

If two plane mirror are kept at an angle w.r.t.
360

1n

each other and an object is kept between them,

then the number of images formed.

1. Write the value of angle of reflection for a ray of light falling normally on a mirror.

2. How does the dispersive power of glass prism change when it is dipped in water?

3. Light falls from glass to air. Find the angle of incidence for which the angle of deviation is 90°.

4. Name the phenomenon due to which one cannot see through fog.

5. What is the ratio of sini and sinr in terms of velocities in the given figure.

i

r

Velocity = v1

Velocity = v2

µ1

µ2

6. What is the shape of fringes in young’s double slit experiment?

7. A equiconcave lens of focal length 15 cm is cut into two equal halves along dotted line as shown
in figure. What will be new focal length of each half.

Page 167

167

21. Produced the truth table for the combination of gates shown in the figure. 3

(B )

Y

A
BA

B

(A )

22. What are the characteristics of the objectives lens of an objective lens of and astronomical
telescope? Derive the expression for the magnifying power of astronomical telescope in normal
adjustment. 3

23. Calculate the de-Broglie wavelength of (i) an electron accelerated by a potential difference of
100V and (ii) a particle of mass 0.03 kg moving with a speed of 100ms–1. Hence show that
wavelength of the particle is not relevant. 3

24. In a plane electromagnetic waves progressing towards –x-axis, the electric field oscillates
sinusoidally at a frequency of 2.0 x 1010 Hz and amplitude 48 Vm–1 along –z-axis. Write the
expression for the electric field and the magnetic field. 3

25. Name the series of hydrogen which does not lie in visible region?

The wavelength of first member of Lyman series is 1216 Å. Calculate the wavelength of third
member of Lyman series. 3

26. The height of a transmission antenna is 600m find the area covered by the antenna in which the
signal from the antenna can be received. 3

27. Draw the circuit diagram to draw the characteristics of common emitter npn transistor. Also draw
the input and output characteristics of the transistor. 3

28. Derive the formula for the equivalent emf and internal resistance of the parallel combination of the
cells of emf E1 and E2 and internal resistance r1 and r2 respectively. Two cells of emf 1V and 2V
and internal resistance 2 and 1 respectively connected in (i) series (ii) parallel. What should
be the value of external resistance in the circuit so that the current through the resistance be the
same in the two cases? In which case more heat is generated in the cells?

OR

Two cells of emf 1.5V and 2.0V and internal resistance 1 and 2 respectively are connected
in parallel so as to send current in the same direction through an external resistance of 5 . (a)
Draw the circuit diagram. (b) Using Kirchhoff’s laws, calculate current through each branch of the
circuit and potential across the 5 resistance.

29. Write the principle, working of moving coil galvanometer with the help of neat labelled diagram.
What is the importance of radial field and phospher bronze used in the construction of moving
coil galvanometer?

OR

Page 168

168

(i) A beam of alpha particular and of protons, enter a uniform magnetic field at right angles
to the field lines. The particles describe circular paths. Calculate the ratio of the radii two
paths if they have same (a) velocity, (b) same momentum, (c) same kinetic energy.

(ii) A beam of -particles and of protons of the same velocity u enters a uniform magnetic
field at right angles to the fields lines. The particles describe circular paths. What is the
ratio of the radii of the two circles?

30. (i) Using the relation for the refraction at a single spherical refracting surface, derive lens
maker’s formula for a thin convex lens.

(ii) The radius of curvature of either face of a convex lens is equal to its focal length. What
is the refractive index of its material?

OR

(i) Deduce the relationship between the object distance, image distance and the focal length
for a mirror. What is the corresponding formula for a thin lens?

(ii) Two lenses of powers +15D and –5D are in contact with each other forming a combination
lens. (a) What is the focal length of this combination? (b) An object of size 3cm is placed
at 30cm from this combination of lenses. Calculate the position and size of the image
formed.

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