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 After completing the module, come back and cross
out the topics that you have revised...

Light (Reflection, Refraction, atmospheric phenomenon)

Types of lens & mirrors, power of lens numerical
Eyes (disease & correction)
Laws of motion & numerical on equation associated with laws
Uniform & Non-uniform motion (graphs & numerical on distance, displacement)
Units; Scalar & Vector quantities
Property of sound; nature of wave; numerical on echo; range of sound
Refractive index & speed relation
Magnetic field lines in different conductors
Work, energy, power, numerical on types of energy, energy consumption,
Relation between energy & momentum
Resistance numerical
 PLANE MIRROR LAWS OF REFLECTION :
The angle of incidence is equal to the angle of reflection.

Image formed by a plane mirror is always virtual The incident ray, the normal to the mirror at the point of
and erect. incidence and the reflected ray, all lie in the same plane.
The size of the image is equal to that of the
object.
The image formed is as far behind the mirror as
the object is in front of it.
The image is laterally inverted.

SPHERICAL MIRRORS
The centre of the reflecting surface of a spherical mirror is a point called the pole. It lies on the surface of the mirror.
This sphere centre is called the centre of curvature of the spherical mirror(C).
Centre of curvature is not a part of the mirror.
The centre of curvature of a concave mirror lies in front of it, it lies behind the mirror in case of a convex mirror.
a straight line passing through the pole and the centre of curvature of a spherical mirror.
This line is called the principal axis.

the radius of curvature is found to

be equal to twice the focal length.
R = 2f
 THE RAY MODEL OF LIGHT
When light rays encounter an object, they can be reflected, absorbed or transmitted.

Transmission is when light

Absorption happens when
Reflection occurs when light passes through a
materials take in light, often
bounces off a surface transparent material, like
converting to heat.
glass or water

Sign Convention for Spherical Mirrors:

i)The object is always placed to the left of the mirror.
(ii) All distances measured from the pole of the mirror.
(iii) All the distances measured to the right are taken as
positive while those measured to the left are taken as
negative.
 Ray diagrams assist us in tracing
the path of light for someone seeing
a point on an image of an item.
Lines represent the incident and
reflected rays with arrows in a ray
diagram. It also aids us in
determining the direction of travel
of light. Rays for the incident and
reflected rays are represented on
the diagram.
Uses of concave mirror

Concave mirrors are commonly used in

torches, search-lights ,vehicles headlights.
They are often used as shaving mirrors to see
a larger image of the face.
The dentists use to see large images of the
teeth of patients.
Large concave mirrors are used to
concentrate sunlight to produce heat in solar
furnaces.

Uses of convex mirror

Convex mirrors are used as rear-view mirrors in vehicles. These
mirrors are fitted on the sides of the vehicle, enabling the driver
to see traffic behind her to facilitate safe driving.

they have a wider field of view as they are curved outwards.

convex mirrors enable the driver to view much larger

LAWS OF REFRACTION OF LIGHT

Magnification: The incident ray, the refracted ray and the
normal to the all lie in the same plane.
h is the height of the object and h′ is the height of the The ratio of sine of angle of incidence to the
sine of angle of refraction is a constant, for the
image
light of a given colour and for the given pair of
The height of the image should be taken as positive media. This law is also known as Snell’s law of
for virtual images. refraction.
The height to be taken as negative for real images. If i is the angle of incidence and r is the angle of
A negative sign in the value of the magnification refraction, then
indicates that the image is real.
A positive sign in the value of the magnification
indicates that the image is virtual.

Mirror formula:

the object distance (u).

the image distance (v).
focal length (f).
 Refractive index
The value of the refractive index for a given pair of
media depends upon the speed of light in the two
media.
light travelling from medium 1 into medium 2, as v1 be
the speed of light in medium 1 and v2 be the speed of
light in medium 2.
The refractive index of medium 2 with respect to
medium 1 is given by the ratio of the speed of light in
medium 1 and the speed of light in medium 2. This is
usually represented by the symbol n21.
This can be expressed in an equation form as
The refraction of light is the bending of light
rays as they pass from one medium to
another, thereby changing the path of the
rays. Refraction occurs due to a change in
the speed of the light ray or wave
Sign convention for lenses :
same as mirrors except focal length of a convex lens
is positive and that of concave lens is negative

Lens formula :

Magnification :

h is the height of the object

h′ is the height of the image

Power of lens :
the ability of a lens to converge or diverge light rays depends on its focal
length. The degree of convergence or divergence of light rays achieved
by a lens is expressed in terms of its power.
The SI unit of power of a lens is ‘dioptre’ D. f is expressed in metres.
power of a convex lens is positive and that of a concave lens is negative.
 BASIC &
DERIVED UNITS

Unit of
Physical Quantity
Measurement

Angle Radian

Frequency Hertz

Force Newton

Weight Newton

Pressure Pascal

Energy Joule

Work Joule

Heat Joule

Power Watt

Electric Charge Coulomb

Potential Difference Volt

Electromotive Force Volt

Electric Resistance Ohm

Electric Capacitance Farad

Electric Conductance Siemens

Inductance Henry

Magnetic Flux Weber

Magnetic Flux Density Tesla

Radioactivity Becquerel
Its lens system forms an image on a light-
sensitive screen called the retina.
Light enters the eye through a thin
membrane called the cornea.
The eyeball is approximately spherical in
shape with a diameter of about 2.3 cm.
Most of the refraction for the light rays
entering the eye occurs at the outer surface
of the cornea.
a structure called iris behind the cornea. Iris
is a dark muscular diaphragm that controls
the size of the pupil.
The pupil regulates and controls the amount
of light entering the eye .
The eye lens forms an inverted real image of
the object on the retina.
The retina is a delicate membrane having
enormous number of light-sensitive cells.
These generate electrical signals. These
signals are sent to the brain via the optic
nerves.
The brain interprets these signals.
Power of accommodation :

The ability of the eye lens to adjust its focal length is called accommodation.
The change in the curvature of the eye lens can thus change its focal length. When the muscles
are relaxed, the lens becomes thin. Thus, its focal length increases. This enables us to see distant
objects clearly.
When looking at objects closer to the eye, the ciliary muscles contract. This increases the
curvature of the eye lens. The eye lens then becomes thicker. the focal length of the eye lens
decreases. This enables us to see nearby objects clearly.
the crystalline lens of people at old age becomes milky and cloudy. This condition is called cataract

Explain human eye defects with diagrams:

 Dispersion :The splitting of light into its
component colours is called dispersion.
Different colours of light bend through
different angles with respect to the
incident ray, as they pass through a prism.
The red light bends the least while the
violet the most. Thus the rays of each
colour emerge along different paths and
thus become distinct. Isaac Newton was
the first to use a glass prism to obtain the
spectrum of sunlight.

Advance sunrise and sunset: this is also due to atmospheric refraction

Blue sky: The molecules of air are more effective in scattering light of shorter wavelengths at the blue
end than light of longer wavelengths at the red end. The red light has a wavelength about 1.8 times
greater than blue light. Thus, when sunlight passes through the atmosphere, the fine particles in air
scatter the blue colour (shorter wavelengths) more strongly than red. If the earth had no atmosphere,
there would not have been any scattering. Then, the sky would have looked dark

Twinkling of stars :
this is due to atmospheric refraction
which occurs in a medium of
gradually changing refractive index.
Since the atmosphere bends starlight
towards the normal, the apparent
position of the star is slightly different
from its actual position.
 The SI unit of electric charge is coulomb
current: net charge Q The SI unit of current is Ampere
time t in milliampere (1 mA = 10–3 A)
current I in microampere (1 μA = 10–6 A).

Potential difference:

Potential difference (V) between two points =

Work done (W)/Charge (Q)
The SI unit of electric potential difference is volt (V)
The voltmeter is always connected in parallel

The potential difference, V directly proportional to the current

Ohm’s law:
flowing through it
R is a constant, and is called its resistance, Its SI unit is ohm
If the resistance is doubled the current gets halved.
A component used to regulate current without changing the voltage
source is called variable resistance.
In an electric circuit, a device called rheostat is used to change the
resistance in the circuit.
Resistance depends upon :

INSULATORS > ALLOYS > CONDUCTORS

 =

APPLICATIONS:
red insulation cover, is called live wire (or positive).
Another wire, with black insulation, is called neutral
wire (or negative). In our country, the potential
difference between the two is 200 V

a current, which changes direction after equal

intervals of time, is called an alternating current .

a direct current (DC) which does not change its

direction with time. a unidirectional current is
produced.

alternating currents is that the direct current always

flows in one direction, whereas the alternating current
reverses its direction periodically.

An important advantage of AC over DC is that

electric power can be transmitted over long distances
without much loss of energy.

Overloading can occur when the live wire and the

neutral wire come into direct contact. In such a
situation, the current in the circuit abruptly increases.
This is called short-circuiting. The use of an electric
fuse prevents the electric circuit and the appliance
from a possible damage by stopping the flow of unduly
high electric current.
If an object travels in a straight line and its velocity increases or decreases by equal
amounts in equal intervals of time, then the acceleration of the object is said to be uniform.
The motion of a freely falling body is an example of uniformly accelerated motion.
On the other hand, an object can travel with non-uniform acceleration if its velocity changes
at a non-uniform rate.
 Equations of Motion
‘u’ is the initial velocity
Acceleration is ‘a’
time is ‘t’
‘v’ is the final velocity
‘s’ is the distance travelled by the object in time ‘t’.

Uniform Circular Motion

When the velocity of an object changes, we say that the object
is accelerating. The change in the velocity could be due to
change in its magnitude or the direction of the motion or both.
If the athlete moves with a velocity of constant magnitude along
the circular path, the only change in his velocity is due to the
change in the direction of motion.
The motion of the athlete moving along a circular path is,
therefore, an example of an accelerated motion.
The circumference of a circle of radius r is given by 2πr . If the
athlete takes t seconds to go once around the circular path of
radius r, the speed v will be,

When an object moves in a circular path with uniform speed, its

motion is called uniform circular motion.
 UNIVERSAL LAW OF GRAVITATION
Every object in the universe attracts every other object with a force which is proportional
to the product of their masses and inversely proportional to the square of the distance
between them. The force is along the line joining the centres of two objects.

G is the constant of proportionality and is called the universal gravitation constant

The SI unit of G is N m2 kg–2.
Value of G is 6.673 × 10–11 N m2 kg–2 .

IMPORTANCE OF THE UNIVERSAL

LAW OF GRAVITATION

The universal law of gravitation successfully

explained several phenomena which were
believed to be unconnected:

(i) the force that binds us to the earth;

(ii) the motion of the moon around the earth;
(iii) the motion of planets around the Sun
(iv) the tides due to the moon and the Sun.
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