CHAPTER
01
ELECTRIC CHARGES AND FIELDS
Class XII
P2
CHAPTER
02
Class XII
ELECTROSTATIC POTENTIAL
AND CAPACITANCE
P4
CHAPTER
07
GRAVITATION
Class XI
P14
CHAPTER
08
RAY OPTICS AND OPTICAL INSTRUMENTS
DISPERSION OF LIGHT
The phenomenon of splitting of white
light into its constituent colours on
passing through a prism.
Class XII
P
REFRACTION THROUGH PRISM
Relation between m and dm
THIN SPHERICAL LENS
Thin lens formula :
f
REFLECTION FROM
PLANE SURFACE
w The image formed by a plane
mirror is laterally inverted.
w The image formed by a plane
mirror is virtual, erect w.r.t.
object and of the same size as the
object.
w If keeping the incident ray fixed,
the plane mirror is rotated
through an angle q, the reflected
ray turns through double the
angle i.e., 2q in that direction.
w Deviation suffered by a light ray
incident at an angle i is given by
d = (180° – 2i)
POWER OF LENSES
Power of lens :
Lens maker’s formula
(Holds for
any curved
spherical
surface)
Angular
spread
O
Y
G
B
I
V
Screen
Mirror formula,
f
Dispersive power,
Magnification, m =
Mean deviation,
If the image is upright or erect with respect to the
object then m is positive. And m is negative if the
image is inverted with respect to the object.
f
Laws of refraction :
w The incident ray, the normal to the interface
at the point of incidence and the refracted
ray all lie in the same plane.
w Snell’s law:
(1m2 = refractive index of medium 2 w.r.t. 1)
f
100
dioptre.
cm, then P =
f (in cm)
SIMPLE MICROSCOPE
Magnifying power
For final image is formed at D (least distance),
Angle subtended by the image at D b
m=
=a =
Angle subtended by the object
at infinity
D
For final image formed at infinity, m =
f
ASTRONOMICAL TELESCOPE
Magnifying power
w For final image is formed at D (least distance),
f
m=
w Power: P = P1 + P2 – dP1P2
(d = small separation between the lense)
w For d = 0 (lenses in contact)
w Power: P = P1 + P2 + P3 + ...
COMMON DEFECTS OF EYES « CORRECTING LENSES
Myopia (short-sightedness)« Concave lens
Hypermetropia (long-sightedness) « Convex lens
Presbyopia « Bifocal lens
Astigmatism « Cylindrical lens
TERRESTRIAL TELESCOPE
For final image is formed at D, m
f
f
For final image is formed at infinity, m
f
f
f
Distance between objective and eyepiece
d = fo + 4f + fe
Angle subtended by the image at D
Angle subtended by the object
at infinity
f
b –f
=a
f
w In normal adjustment, image formed at infinity
m = – fo / fe
COMBINATION OF LENSES
A terrestrial telescope
Light from
object at
infinity
Inverted image
Upright image
Erecting lenses
Objective lens
P16
TOTAL INTERNAL REFLECTION
The phenomenon in which a ray of light
travelling from an optically denser into
an optically rarer medium at an angle of
incidence greater than the critical angle
for the two media is totally reflected
back into the same medium.
TIR conditions
w Light must travel from denser to rarer.
w Angle of incidence is greater than
critical angle.
REFRACTION OF LIGHT
RAY OPTICS
&
OPTICAL
INSTRUMENTS
REFLECTION OF LIGHT
Laws of reflection:
w The angle of incidence i equals the angle of
reflection r.
Ði = Ðr
w Incident ray, the normal and the reflected
ray lie in the same plane.
w If i < ic, then refraction takes place.
w If i = ic, then grazing emergence takes
place.
w If i > ic, then total internal reflection
takes place.
R
REFLECTION BY SPHERICAL MIRRORS
for the lens placed in air
w The SI unit of power of lens is
dioptre (D).
w For a convex lens, P is positive.
w For a concave lens, P is negative.
w When focal length (f) of lens is in
w
w
w
w
i
Q
or d = (m – 1)A (Prism of small angle)
Angular dispersion = dV – dR = (mV – mR)A
1 æ mdenser - mrarer ö æ 1
1 ö
=
÷ø çè R - R ÷ø
f çè
mrarer
1
2
(e– r 2)
d
N2
e
r
r
F 1q 2G
N
H
(i– r1)
E
where,
dm = angle of minimum
deviation
A = angle of prism
REFRACTION BY SPHERICAL SURFACE
Relation between object distance (u), image
distance (v) and refractive index (m)
Magnification:
N1
le
ib
Vis
A
Deviation
of red light(dR)
Deviation of
R violet light (dV)
t
ligh
RELATION BETWEEN m AND iC
The angle of incidence in the optically
denser medium for which the angle of
refraction is 90°. It is denoted by ic.
Eyepiece
COMPOUND MICROSCOPE
Magnifying power, m = mo × me
For final image formed at D (least distance)
m=
b vo
=
a uo
Dö L
æ
çè1 + f ÷ø = f
e
0
Dö
æ
çè1 + f ÷ø
e
APPLICATIONS OF TIR
w
w
w
w
w
w
Fiber optics communication
Medical endoscopy
Periscope (Using prism)
Sparkling of diamond
Mirage
Totally reflecting glass prisms
REFRACTIVE INDEX
Real and apparent depth
For final image formed at infinity
m=
f
f
Newtonian reflecting telescope
REFLECTING TELESCOPE
Magnifying power
When the final image is formed at D,
f
f
m = o 1+ e
fe
D
When the final image is formed at infinity
f
m=
f
f
(
(
Eyepiece lens
Objective mirror
Telescope
tube
Light
Diagonal mirror
CHAPTER
09
WAVE OPTICS
Class XII
P18
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