•Light follows a rectilinear propagation (3 * 108 m/s)

•Umbra → Point source of light → Shadow (Total dark)

•Penumbra →Extended source of light → Shadow (Partial dark)

It represents the phenomenon of :

Light is a form of energy that provides visual sensations in our eyes. Light is an electromagnetic wave that is transverse in nature. The speed of light in a vacuum is 3*10^8 m/s which is the highest and all other medium decreases the speed of light.

REFLECTION REFRACTION INTERFERENCE DIFFRACTION SCATTERING

LAW OF REFLECTION

Frequency, Speed, Wavelength

DO NOT CHANGE

PHASE Changes

MIRRORS

PLANE MIRROR

Size of image = Size of objectMin. size of mirror to view complete object is HALF

POWER OF PLANE MIRROR ?

Focal length= infinityPower= 0

Linear Magnification= 1

When 2 mirrors are kept facing each other at angle θ, and object is placed between them,No. of images=

CONCAVE & CONVEX MIRRORSSPHERICAL MIRROR

Concave Mirrors Torch,VehicleheadlightsShaving mirrors,DentistMirrorConc. sunlight to produce heat

Convex mirrors Rear view mirrorsAlways gives erect though diminished imageProvides wider view

Use of Concave & Convex Mirrors

1/f = 1/v + 1/u

m=

MIRROR FORMULA

LINEAR MAGNIFICATION

‘+’ magnification means image is virtual and erect‘-’ magnification means image is real and inverted

Refraction•Velocity is higher in less denser medium

•n21 = v1/v2 (n21 → refractive index of medium 2 wrt medium 1)

•A ray of light will bend towards the normal if it is travelling from rarer to

denser medium & away from the normal if it is

travelling from denser to rarer medium

Frequency, PHASEDO NOT CHANGE

Speed, Wavelength Changes

Few examples of refraction

•Twinkling of stars

•Sunrise & sunset (we can see the sun 2 min before the

sunrise & 2 min after the sunset)

•Bottom of water filled body appears to be raised

Concave & Convex Lenses

•Convex Lens –

Converging Lenses

Power – Positive

•Concave Lens –

Diverging Lenses

Power – Negative

Power of a lenses → Diopter

IMAGE FORMED BY CONCAVE LENS

Image formation by Concave Lens

Object Location Image Location Image Nature Image Size

Infinity At F2 Virtual and ErectHighly Diminished

Beyond Infinity and Zero

Between F1 and Optical center

Virtual and Erect Diminished

IMAGE FORMED BY CONVEX LENS

Image formation by Convex Lens

Object location Image location Image nature Image size

Infinity At F2 Real and Inverted Diminished

Beyond 2 F1 Between 2F2 and F2 Real and Inverted Diminished

Between 2F1 and F1 Beyond 2F2 Real and Inverted Enlarged

At F1 At infinity Real and Inverted Enlarged

At 2 F1 At 2F2 Real and Inverted Same size

Between F1 and 0On the same side as the object

Virtual and Erect Enlarged

1/v - 1/o = 1/fLENS FORMULA

Magnification (m) = h'/h MAGNIFICATION

P = 1 FPOWER OF LENS

IMPORTANT CONDITIONS :

Two lenses in contact;m=m1 x m2P= P1 + P2

If 2 lens of equal focal length, opp. Nature combines, it will act as plane …..f= ..?

If lens is dipped in liquid(of higher refractive index), lens will behave opposite…

Violet colour deviates maximumRed colour min.

Colour of object is determined by colour reflected by it

Total Internal Reflection•Light can not always pass through denser to rarer medium

•if the angle of incidence > critical angle, it leads to total reflection of light

•Examples : Optical fiber, Mirage effect (Usually associated with hot deserts)

Critical Angle can be described as the angle of incidence that offers an angle of refraction of 90 degrees.

Mirage Effect

•Air near desert surface is

hot & which cools rapidly

with height (2 different

mediums density wise)

•Rays from top of trees

exceeds critical angle & TIR

occurs

•Observer sees tree upside

down giving illusion of water

•Vice a versa if air near the

ground is cold & up above

hot

Rainbow

•Formed opposite of

sun

•Process →Refraction

& Dispersion + TIR +

Refraction &

Dispersion

Scattering of Light•A molecule of a medium emits

incoming light in all possible directions

known as scattering (Tyndall Effect)

Blue Color Sky

•When sunlight reaches earth’s

atmosphere, Blue color scatters more

strongly than the red

•When this scattered color enters our

eye, sky looks blue to us

Sky appears RED at sunrise and sunset

RED colour of signal lightIf earth had no atmosphere, no scattering

Interference of wavesSuperimposition of 2 waves of same kind

which passes through same point at the same

time

Constructive interference – Same

phase interference

Destructive interference – Opposite

phase interference

Example → Colors in soap bubble & oil on

water in presence of white light (Alternate

black & white spots in case of

monochromatic light)

POLARISATION IS ONLY PHENOMENON WHICH PROVES TRANSVERSE NATURE OF LIGHT

Diffraction•Spreading of light through a narrow

slit or aperture

•Failure of light to travel in a straight

line (due to the wave nature of light)

Diffraction Grating →A device used

to cause diffraction for ex. Parallel

equidistant lines on glass or metals (as

in CD)

Holograms → Result of Laser +

Interference + Diffraction

The lens of eye forms an inverted real image of an object on the

retina.

Defects of Vision and Their Correction•When the crystalline lens of an eye normally at old age, becomes milky

and cloudy, it is known as cataract.

PresbyopiaPresbyopia, an eye problem, arises because of the gradual weakening of

the ciliary muscles and diminishing flexibility of the eye lens.

Some people suffer from both myopia and hypermetropia; such kind of

eye defect is treated by using bifocal lenses.

A common type of bi-focal lenses consists of both the concave and the

convex lenses.

Myopia•Myopia is also known as

near-sightedness.

•A person suffering from

myopia can see nearby

objects clearly, but cannot

see distant objects clearly.

•in a myopic eye, the

image of a distant object

is formed in front of the

retina instead of at the

retina.

•This defect can be

corrected by using

a concave lens of

suitable power.

Hypermetropia•Hypermetropia is also known as far-

sightedness.

•A person suffering from hypermetropia

can see the distant objects clearly, but

cannot see the nearby objects clearly.

•Hypermetropia can be corrected by

using a convex lens of appropriate

power.

Cathode rays are the beam of electrons travelling from the negatively-charged

cathode to the positively charged anode at the other end of the vacuum tube.Property 1: Cathode rays travel in a straight line and can cast sharp shadows.Property 2: Cathode rays are negatively charged.Property 3: Electric field and magnetic field deflect cathode rays.Property 4: They are produced at the cathode (negatively charged electrode) and travel towards the anode (positively charged electrode) in a vacuum tube.Property 5: The properties of the cathode rays do not depend on the electrodes and the gas used in the vacuum tube.Property 6: Speed of cathode rays is slower than light.Property 7: The objects hit by cathode rays get heated.Property 8: They can penetrate through thin metal plates.Property 9: Phosphors glow when cathode rays fall on them.Property 10: Gas gets ionized by cathode rays.Property 11: Cathode rays are 1800 times lighter than hydrogen, the lightest element.

Radio: A radio basically captures radio waves that are transmitted by radio stations. Radio waves can also be emitted by gases and stars in space. Radio waves are mainly used for TV/mobile communication.Microwave: This type of radiation is found in microwaves and helps in cooking at home/office. It is also used by astronomers to determine and understand the structure of nearby galaxies and stars.Infrared: It is used widely in night vision goggles. These devices can read and capture the infrared light emitted by our skin and objects with heat. In space, infrared light helps to map the interstellar dust.X-ray: X-rays can be used in many instances. For example, a doctor can use an x-ray machine to take an image of our bone or teeth. Airport security personnel use it to see through and check bags. X-rays are also given out by hot gases in the universe.Gamma-ray: It has a wide application in the medical field. Gamma-ray imaging is used to see inside our bodies. Interestingly, the universe is the biggest gamma-ray generator of all.Ultraviolet: Sun is the main source of ultraviolet radiation. It causes skin tanning and burns. Hot materials that are in space also emit UV radiations.Visible: Visible light can be detected by our eyes. Light bulbs, stars, etc. emit visible light.

Protons Discovered by Goldstein

Neutrons > Protons > Electrons (in terms of mass)

Electrons Discovered by Thomson

Neutrons Discovered by Chadwick

Model of an atom

Radioactivity•When size of nucleus enlarges → Electrostatic force > Nuclear force,

which leads to radioactivity

•Unstable atomic nuclei will spontaneously decompose to form nuclei with

a higher stability.

•The decomposition process is called radioactivity. The energy and

particles which are released during the decomposition process are called

radiation.

•When the unstable nuclei are prepared in the laboratory, the

decomposition is called induced radioactivity.

•When unstable nuclei decompose in nature, the process is referred to as natural radioactivity.

Three major types of natural radioactivity

Alpha radiation

•Consists of a stream of positively charged particles, called alpha particles

•Alpha particles have an atomic mass of 4 and a charge of +2 (a helium

nucleus).

•When an alpha particle is ejected from a nucleus, the mass number of the

nucleus decreases by four units and the atomic number decreases by two

units. For example:238

92U → 42He + 234

90Th (The helium nucleus is the alpha particle)

Beta Radiation

•Consists of a stream of electrons, called beta particles.

•When a beta particle is ejected, a neutron in the nucleus is converted to a

proton, so the mass number of the nucleus is unchanged, but the atomic

number increases by one unit. For example:234

90Th → 0-1e + 234

91Pa (The electron is the beta particle)

Gamma Radiation

•Gamma rays are high-energy photons with a very short wavelength

(0.0005 to 0.1 nm).

•The emission of gamma radiation results from an energy change

within the atomic nucleus.

•Gamma emission changes neither the atomic number nor the atomic

mass.

•Alpha and beta emission are often accompanied by gamma emission,

as an excited nucleus drops to a lower and more stable energy state.

Applications of Radioactivity•Used as a tracer for chemical reactions. You can put an isotope in a living

organism and it will do the same reactions as the regular element but you

will be able to trace what it reacts with and where it goes

•Detecting how old something is by seeing how much of the isotope of the

element is left → Carbon Dating → C 14 (Used for living organisms) &

Uranium dating → For non-living organism ex. rocks

•Used for finding out the faults in metal structures esp. in

airplanes → radioactive material will penetrate more through the cracked

areas

•Act as a fuel for nuclear reactors to produce electricity

•Some isotopes are used in the treatment of cancer→ to kill the cancer

mutated cells

•Some isotopes are used to study the proper functioning of internal organs

•Gamma radiations are used to sterilize the surgical instruments

•Radio phosphorous is used for studying the rate of phosphorous

assimilation by the plant

•Preservation of food grains and seeds

•Used for preparing synthetic elements (artificial transmutation)

•Detecting leaks in natural gas pipes

Nuclear fission

•In nuclear fission the nucleus of an atom breaks up into two

lighter nuclei.

•The process is accompanied by the release of a large

amount of energy.

•The process may take place spontaneously in some cases

or may be induced by the excitation of the nucleus with a

variety of particles (e.g., neutrons, protons, deuterons, or

alpha

particles) or with electromagnetic radiation in the form

of gamma rays.

Atomic bomb → Only by fissile U 235 i.e. Enriched

Uranium (90%)

For Nuclear reactors → 6 % of U-235

Nuclear fusion

•Process by which nuclear reactions between light elements form heavier elements (up

to iron).

•During this process, matter is not conserved because some of the matter of the fusing

nuclei is converted to photons (energy) → substantial amounts of energy are released.

Hydrogen bomb → Requires an atomic bomb to detonate

Fission Controlled chain reaction of U 235 or Plutonium 239

ModeratorsD2O, H2O, Solid Graphite (To slow down neutrons bombardment & start a chain reaction)

Heat Generation → Rotation of turbines → Powering

Generator → Electricity through cable lines

Cooling Liquid sodium

Control

RodsCadmium (Which absorb excess neutrons)

Physical Quantity Symbol(s) Scalar/ Vector SI Unit

Mass m Scalar Kilogram (Kg)

Time t Scalar Seconds (s)

Distance, Length l, d, r Scalar Meter (m)

Area A Scalar m2

Volume V Scalar m3

Density D Scalar kg/m3

Temperature T Scalar Kelvin (K)

Frequency f, v Scalar Hertz (Hz)

Heat Q Vector Joule (J)

Specific Heat Capacity c Scalar J kg−1

K−1

Wavelength λ Scalar meter (m)

Angular Displacement θ Scalar Radian (rad)

Speed of light & sound c Scalar m/s

Angular frequency ω Pseudovector Radian per second (rad/s)

Physical Quantity Symbol(s) Scalar/ Vector SI Unit

Velocity v Vector m/s

Acceleration a Vectormeters per second squared (m/s2)

Angular acceleration α Vectorradian per second squared (rad/s2)

Momentum p Vector kg⋅m/s

Period T Scalar S or sec

Force F Vector Newton (N)

Torque T Vector N⋅m

Power P Scalar Watt (W)

Mechanical Work W Scalar Joule (J)

Energy E Scalar Joule (J)

Pressure p Scalar Pascal (Pa)

Moment of Inertia I Scalar kg m2

Angular Momentum L Vector kg⋅m2s-1

Friction f Vector Newton (N)

Coefficient of Friction µ Scalar unitless

Kinetic Energy K Scalar Joule (J)

Potential Energy U Scalar Joule (J)

Physical Quantity Symbol(s) Symbol Name Scalar/ Vector SI Unit

Charge q, Q – scalar Coulomb (C)

Current I – scalar Ampere (A)

Resistance R – scalar Ohms (Ω)

Inductance L – scalar Henry (H)

Capacitance C – scalar Farad (F)

Electric Potential Difference

V – scalar Volt (V)

Electric Field E – Vector Newton per coulomb (N C

-1)

Magnetic Field B – Scalar Tesla

1st Law of Motion

Why does a man getting off a moving bus fall down?

1.He falls because of his habit of leaning forward

2.Due to inertia of motion, the upper body continues to be in motion in the forward direction but the feet comes to rest as soon as they touch the ground

3.Due to inertia of rest, the road is left behind and the man reaches forward

4.Due to all of the reasons stated above

3

2nd Law of Motion

Conservation of Momentum

p= mv

Recoil of Gun

Rocket

Balloon 4

1. A coin dropped in the lift takes time T1 to reach the floor when the lift is stationary and time T2 when the lift

moves with constant acceleration. Which of the following relation is true ?

1.T1> T2

2.T2> T1

3.T1= T2

4.T1>> T2

5

Newton’s3rd Law of Motion

What is Friction?Friction is defined as the resistance offered by the surfaces that are in contact when they move past each other.

1. On the nature of the two surfaces that are in contactFriction is dependent on the smoothness or roughness of the two surfaces that are in contact with each other. When the surface is smooth, the friction between the two reduces as there is no much interlocking of irregularities taking place. While the surface is rough, friction increases.

2. On the force that is acting on these surfacesFriction increases when the force is applied along the irregularities.

Factors Affecting Friction

Applications of Friction•Friction finds application when matchsticks are ignited.•Motion of pistons in a cylinder is an application of friction.•It is possible to write on books and board as there is friction between pen and the board.

Methods to reduce friction•For objects that move in fluids such as boats, planes, cars, etc, the shape of their body is streamlined in order to reduce the friction between the body of the objects as the fluid.•By polishing the surface, as polishing makes the surface smooth and friction can be reduced.•Using lubricants such as oil or grease can reduce the friction between the surfaces.•When objects are rolled over the surface, the friction between the rolled object and surface can be reduced by using ball bearings.

Angular Velocity ω=Θ/tWhere ω is the angular velocity, θ is the angular displacement, and t is the change in time t

Angular Velocity of a planet increases when it comes closer to sun

S= v x t

The SI unit of angular velocity is radians per second (rad/s).

ω=θ/t

Angular Acceleration

Where,•ω = Angular Velocity•θ = Angle Rotated•t = Time Taken

In SI units, angular acceleration is measured in radians per second squared (rad/s2) and is usually denoted by the alpha (α).

F=mac =mv /rWhere,•F is the Centripetal force.•ac is the Centripetal acceleration.•m is the mass of the object.•v is the speed or velocity of the object.•r is the radius.

2

•Turning a car: Here the centripetal force is provided by the frictional force between the ground and the wheels.•Going through a loop on a roller coaster: The force is provided by the Normal Force as the seat or wall pushes you toward the centre.•Planets orbiting around the Sun: Centripetal Force is provided by Gravity.

•Spinning a ball on a string or twirling a lasso: Here the centripetal force is provided by the force of tension on the rope pulls the object in toward the centre.

Centripetal Force

Centrifugal Force

Where,•Fc is the Centrifugal force•m is the mass of the object•v is the velocity or speed of the object.•r is the radius.

F=mac =-mv /r2

•Weight of an object at the poles and on the equator•A bike making a turn.•Vehicle driving around a curve•Equatorial railway

Centrifugal Force Centripetal Force

If an object moving in a circle and experiences an outward force then this force is called the centrifugal force.

If the object travels at a uniform speed in a circular path it is called centripetal force.

The object has the direction along the centre of the circle from the centre approaching the object

The object has the direction along the centre of the circle from the object approaching the centre.

Mud flying of a tire is one example of the centrifugal force.

A satellite orbiting a planet is an example of the centripetal force.

WorkW=F.dW=F.d.cos θWhere,•F is the force applied•d is the displacement•θ is the angle between force and direction of motion

SI Unit- Nm.

Kinetic energy is the energy possessed by a body due to its motion.

Where,mass of the body = m,the velocity with which the body is travelling is v.SI Unit- Kgm2/s2

Kinetic Energy Examples•A truck travelling down the road has more kinetic energy

than a car travelling at the same speed because the truck’s mass is much more than the car’s.

•A river flowing at a certain speed comprises kinetic energy as water has a certain velocity and mass.

•The kinetic energy of an asteroid falling towards earth is very large.

•The kinetic energy of the aeroplane is more during the flight due to large mass and speedy velocity.

W = m×g×h = mgh

Potential EnergyThe formula for potential energy depends on the force acting on the two objects.

Where,•m is the mass in kilograms•g is the acceleration due to gravity•h is the height in meters

SI Unit- kg m2 / s2

All energy has the same units – kg m2 / s2, and is measured using the unit Joule (J).

PowerThe capacity to do work is termed Energy.

P=W/t

Where,Work done = WTime taken= t

In any electrical circuit, the power is computed making use of these three formulasIn regard to Voltage and current, it is articulated asP = V×IIn regard to current and resistance, it is articulated asP = I2RIn regard to voltage and resistance, it is articulated asP=V2R Where,A voltage applied across the two ends =V,Current flowing in the circuit = I andResistance = R.

Symbol

The angular momentum is a vector quantity, denoted by →LL→

UnitsIt is measured using SI base units: Kg.m2.s-1

Dimensional formulaThe dimensional formula is: [M][L]2[T]-1

Ice-skaterWhen an ice-skater goes for a spin she starts off with her hands and legs far apart from the center of her body. But when she needs more angular velocity to spin, she gets her hands and leg closer to her body. Hence, her angular momentum is conserved, and she spins faster.

Newton’s Law Of Universal GravitationNewton’s Law of Universal Gravitation states that every particle attracts every other particle in the universe with a force

that is directly proportional to the product

of the masses and inversely proportional to the square of the distance between them.

F∝m1m2/r2⇒F=Gm1m2r2

The value of G is found to be G = 6.673 x 10-11 N m2/kg2.

Funda of ‘g’

The value of ‘g’ is maximum at surface

What if, Earth stops rotating ??

6

Funda of ‘Lift’

Uniform SpeedNo change

AccelerationUp- more weightDown- less weight

If rod is brokenWeight= 0, weightlessness 7

A person standing in the elevator finds his weight to be lesser than his actual weight in which of the following cases?

1.When the elevator moves upward with constant acceleration

2.When the elevator moves downward with constant acceleration

3.When the elevator moves upward with constant velocity

4.When the elevator moves downward with constant velocity

T=F/L

The ratio of the surface force F to the length L along which the force acts.

Surface Tension

It decreases with increase in temp.

8

Oil spreads over the surface of water whereas water does not spread over

1. Surface tension of water is very high

2. Surface tension of water is very low

3. Viscosity of oil is high

4. Viscosity of water is high

Hooke’s LawHooke’s law states that the strain of the material is

proportional to the applied stress within the elastic limit of that

material.

When the elastic materials are stretched, the atoms and molecules deform until stress is applied, and when the stress is removed, they return to their initial state.Mathematically, Hooke’s law is expressed as:

F = –kxIn the equation,F is the force, x is the extension length, k is the constant of proportionality known as spring constant in N/m.

Pressure•The force, applied on a unit area of a surface is known as pressure

•Pressure=force/area

On which it acts•If the area is smaller, then the pressure on a surface would be greater;

e.g. this is the reason that the area of one end of a nail is pointed to exert

sufficient pressure to exert sufficient pressure

The SI unit of pressure is PascalPascal Formula:

Pressure exerted by liquid at depth h below the surface of liquid is:

p= hdg

d= density of liquid

Measured ny manometer

Boiling point increases with increasing pressure

Atmospheric PressureMeasured by Barometer

Decreses with altitude

Pascal’s Law

“The external static pressure applied on a confined liquid

is distributed or transmitted evenly throughout the liquid

in all directions”.

Application of Pascal’s law

Hydraulic lift •Hydraulic jack and hydraulic press.

•Hydraulic Brakes for increasing resisting force in the vehicle braking systems.

•Artesian wells, water towers, and dams.

•Aircraft Hydraulic System: to slow down aeroplanes on the runway. Also, used in

flight control mechanism, landing gears, etc.

•Hydraulic Pumps

•Wide applications of Pascal’s law are also seen in hydraulic testing of pressurized

tanks, calibration of pressure gages, pressing of oils such as olive, hazelnut, and

sunflower oils, compression of wood stocks, etc.

•Various Pneumatic devices like Dentists’ drills, jackhammers, paint sprayers, and

air brakes on trucks, etc works on the principle of Pascal’s Law.

•It refers to the law of buoyancy (the ability or tendency of

something to float in water or other fluids).

•According to the principle, when an object is completely or

partially submerged in a fluid, whether gas or liquid, it is acted

upon by an upward force (buoyancy) equal to the weight of

the fluid it has displaced.

•The force acting downward on the object is the weight of the

object. The upward force is the one given by the Archimedes

Principle.

•The difference between the two forces is the net force acting

on the object.

•If the buoyant force is more than the weight, the object rises;

if it is less, the object sinks.

•If the net force is zero, the object remains in place, and

neither rises nor sinks.

‘Archimedes Principle’

Applications of Archimedes’ Principle1. Ships

2. Beach Balls

3. Submarines

4. Floating

5. Hydrometer

6. Swimming

7. Hot Air Balloon

8. Lactometer

9. Geology

10. Fish

Density is the measurement of how tightly a material is packed together. It is

defined as the mass per unit volume.

Density Symbol: D or ρ

Density Formula: ρ = m/V, where ρ is the density, m is the mass of the object and V is the volume of the object.

Relative density = Density of substance/ Density of water at 4∘C

= Weight of substance in air/ Loss of

weight in water

Relative Density unit:

Relative density has no unit because it is the ratio of same units which gets

cancelled.

Measured by hydrometer

Density of water is max. at 4degree celcius

Why it is easier to swim in sea water ?Density of sea water > density of normal water

Bernoulli’s PrincipleThe total mechanical energy of the moving fluid comprising the

gravitational potential energy of elevation, the energy associated with the

fluid pressure and the kinetic energy of the fluid motion, remains

constant.

p + 1/2ρv2 + ρgh =constant

Bernoulli’s equation formula is a relation between pressure, kinetic energy, and gravitational potential energy of a fluid in a container.

Where,•p is the pressure exerted by the fluid•v is the velocity of the fluid•ρ is the density of the fluid•h is the height of the container

Capillary action is the force or an effort made to push the liquid by fighting the gravitational force of

attraction. Also, after a certain amount of time, the liquid falls. This fall occurs when the liquid faces a surface tension.

Real-life applications:

1.When we pour the kerosene oil in a lantern and the melted wax in a candle, the capillary action forms in the cotton wick

and burns.

2.The coffee powder gets dissolved in water easily because water immediately wets the fine granules of coffee by the action

of capillarity.

3.The water poured into the grassland rises in the uncountable capillaries formed in the stems (Xylem) of plants and trees

and reaches the leaves.

4.The tip or the nib of a pen splits to provide capillary action for the ink to rise, which helps us to write on the paper.

5.After taking a bath, we use a towel, the action of a towel in soaking up moisture from the body is due to the capillary

action; also known as capillary water.

Viscosity

Viscosity is a measure of a fluid’s resistance to flow.

The SI unit of viscosity is poiseiulle (PI).Its other units are newton-second per square metre (N s m-2) or pascal-second (Pa s.) The dimensional formula of viscosity is [ML-1T-1].

The viscosity of liquids decreases rapidly with an increase in temperature, and the viscosity of gases increases with an increase in temperature. Thus, upon heating, liquids flow more easily, whereas gases flow more slowly. Also, viscosity does not change as the amount of matter changes.

IMP. CONCEPTS- SIMPLE PENDULUM

Time period of a simple pendulum of infinite length is 84.6 min.

A pendulum clock gets slower in summerFaster in winter ??

At moon, T will increase

Funda of ‘Lift’ wrt. SIMPLE PENDULUM

AccelerationUp- T will decreaseDown- T will increase

If rod is brokenInfinite time

7

Light Emitting Diode (LED) converts

a. Light energy into electrical energy

b. Electrical energy into light energy

c. Thermal energy into electrical energy

d. Mechanical energy into electrical energy

Solution. A light-emitting diode (LED) is a two-lead semiconductor light source that resembles a

basic pn-junction diode, except that an LED also emits light.

The Celsius temperature is a/an

a. Relative temperature

b. Absolute temperature

c. Specific temperature

d. Approximate temperature

Solution. The degree Celsius (°C) can refer to a specific temperature on the Celsius scale as well as a unit

to indicate a temperature interval, a difference between two temperatures.

Absolute temperature is the temperature of an object on a scale where 0 is taken as absolute zero, or the

temperature where there is zero thermal energy in a sample of matter.

The gas used in a refrigerator is

a. Cooled down on flowing

b. Heated up on flowing

c. Cooled down when compressed

d. Cooled down when expanded

Solution. Adiabatic cooling occurs when the pressure of a substance is decreased as it does work on its

surroundings. Expansion decreases pressure.

Which type/types of pen uses/use capillary action in addition to gravity for flow of ink?

a. Fountain pen

b. Ballpoint pen

c. Gel pen

d. Both ballpoint and gel pen

Solution. Capillary action (sometimes capillarity, capillary motion, or wicking) is the ability of a liquid to

flow in narrow spaces without the assistance of, and in opposition to, external forces like gravity, fountain

pen uses this action.

A device, which is used in our TV set, computer, radio set for storing the electric charge, is

a. Resistor

b. Inductor

c. Capacitor

d. Conductor

Solution. A capacitor (originally known as a condenser) is a passive two-terminal electrical component

used to store energy electrostatically in an electric field.

When deep sea fishes are brought to the surface of the sea, their bodies burst. This is because the blood in their bodies flow at very

a. High speed

b. High pressure

c. Low speed

d. Low pressure