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Physics Important notes for SSC CGL / CHSL exam : GK

Physics Important notes for SSC CGL / CHSL exam : GK

Physics Important notes for SSC CGL / CHSL exam : GK


  • Speed of light is maximum in vacuum.
  • Longitudinal waves can’t be polarized.
  • Rainbow are always formed in direction opposite to the sun.
  • The frequency of visible light varies between 400 nm to 700 nm.
  • Colour blindness was first discovered by Homer (1976).
  • Focal distance of tens is maximum for red light and minimum for violet fight
  • 3-D Image is known as hologram.
  • If a transparent material is invisible in any liquid, then both of them have the same refractive index.
  • Magnifying glass is convex lens of small focal length­s’- If two mirrors are at an angle of 75° then the number of images is 5.
  • Human eyes have convex lens.

Physics Important notes

  • Raman Effect is related to scattering.
  • Optical fibers works on the principle of total internal reflection.
  • Hypo or radium thiosulphate is used for fusing in photography.
  • Power of sunglass is zero.
  • Heat energy are transmitted as infra-red rays.
  • The first use of telescope for research was by Galeleo Galilie of Italy in 1609.
  • Power measures the degree of divergence or convergence and is mea­sured in diopetres.
  • Negative sign denotes divergence or a concave lens.
  • Positive sign is for convergence or a convex lens.
  • Air bubble in water behaves as concave lens.
  • As temperature of medium increases, its refractive index increase.
  • Refractive index of a material is independent of angle of incidence.
  • The angle of deviation in refractions is given by d = (i – r),i = angle of incidence and r = angle of refraction.
  • 100°C = 212°F = 373 K=80R
  • Bolometer is used for detection of infra-red rays.
  • Specific heat of water is 1.0 calorie/gm-°C.
  • Two thinner blankets are more warmer than a single blanket equal to their width.
  • Colour cloths are good absorber of heat.
  • Ammonia is used as a coolant in refrigerator.
  • If there is a relative motion between the source and the observer, then the frequency of sound heard by the observer might be different from the frequency of the source. (Doppler’s effect).
  • Echo forms due to reflection of sound.
  • When two sound sources of nearly same frequency are played together. then beats occur.
  • Number of beats per sound equal to difference between the frequen­cies of sources.
  • The frequency of sound produced byy supersonic engines are above au­dible range.
  • The same note from ‘Sitar” and ‘Veena’ have different quality.
  • There is a coating of iron oxide on tape used in tapere-corder.
  • The pitch of sound depends upon the frequency. If n is the frequency of open organ pipe and we close an end of the organ pipe, then the frequency will be n/2
  • At room temperature velocity of sound is 330 m.
  • There is no change in velocity, wavelength and frequency of refractive wave.
  • Audible frequency ranges from 20Hz to 20,000 Hz.
  • There is no change in frequency of sound when it changes medium but its velocity, direction and intensity will be changed.
  • The direction of wave is independent of velocity, wavelength and frequency.
  • The velocity of sound is increased with increasing density of the medium.
  • Sensation of sound is for 1/10 second.
  • Receiver of telephone converts electrical energy into sound energy.
  • Wave is formed by repeated vibrations of particles of medium in which the wave is formed.
  • Pulse is a wave set up by single disturbance of short duration.
  • The change in frequency due to Doppler’s effect is dependent on the velocities of observer and source.
  • A stationary wave is characterized by the appearance of nodes and an­tinodes.
  • There is a decrease of 2 in atomic number and decrease of 4 in mass number after emission of an a particle.
  • There is an increase of 1 in atomic number after emission of a P particle.
  • There is no effect of y radiation upon atomic as well as mass number.
  • Neutron was discovered by Chadwick.  Important physics notes by Pinnacle
  • Carbon dating is used in determining age of fossils.
  • Atomic mass unit (amu) is equal to — of the mass of
  • 1 amu = 1.6 kg  1 amu = 931 MeV
  • Binding energy is the amount of energy required to separate each nucle­ons from the nucleus.
  • In nuclear fission, a greater nuclei is broken into smaller nuclei and there is a huge amount of energy released. Atom Bomb works on nuclear fission.
  • When two or more smaller nuclei are jointed together to form a large nuclei, the process is called nuclear fusion. A great amount of energy is released. Hydrogen bomb works on principle of nuclear fusion. Nuclear fusion is the source of the Sun’s energy.
  • Cadmium is a good absorber of neutrons, used as controller in atomic reaction.
  • Nuclear reactor is used for controlled chain reaction.
  • Heavy water. Graphite or Berilium oxide are used as moderator in nuclear reactor. (: heavy water).
  • Polonium is first human made element.
  • Mass of neutron is slightly greater than that of proton.
  • Elements having atomic number greater than 83 must be radioactive.
  • Cobalt-60 is normally used in radiation therapy.
  • Before X-ray, Barium is given to the patient because Barium is good absorber of X-ray radiation.
  • X-rays is used for determing structure of crystals.
  • V The unit of Plank’s is J/S,
  • Proton is ionized hydrogen atom.
  • Cryogenic engine is used in space shuttle.
  • Titanium is known as metal of future.
  • Uranium oxide is known as yellow cake.
  • Tritium is radioactive isotopes of Hydrogen.
  • Tuning of radio is an example of resonance.
  • Cobalt-60 is used in Leukemia treatment
  • Cybernetics is study of communication between human and machine.
  • The filament of Halogen lamp is made of tungsten-iodine mixture.
  • Ceramic is used in Super-conductivity.
  • A transformer which increases the applied e.m.f. of an alternating cur­rent is called Step-up transformer.
  • transformer, which decreases applied e.m.f. of alternating current is called step-down transformer.
  • A device which convert mechanical energy into electric energy is called dynamo. However, if it produces a fairly large amount of power, it is called Generator.
  • Generator is based on the principle of electromagnetic induction.
  • in generator, armature consists of laminated soft iron core, from the centre of which passes a steel axle.
  • Slip sings of generator are made of gun metal.
  • Brushes of generator are made out of carbon or gun metal.
  • Coulumb is the unit of electric charge (coulumb = ampere/second).
  • 1 coulumb = 6.25
  • Magnetic effect of electric current was discovered by Weston.
  • Ammeter is used in DC as well as in AC. Important physics notes by Pinnacle
  • Resistance of Ammeter is very low.
  • Resistance of Voltmeter is very high.
  • Volmeter measures potential difference between two points.
  • A parallel combination of a galvanometer and a small resistance is equivalent to an ammeter.
  • A series combination of a galvanometer and a high resistance is equivalent to a voltmeter.
  • Ammeter is always connected in series while voltmeter is always con­nected in parallel.
  • Electron volt is the unit of energy.
  • 1 ev = 1.6J
  • Watt is the unit of electric power, watt = volt x ampere =
  • Kilowatt hour (KWH) is also the unit of electric power 1 KWH = 3.6 x J
  • The resistance of low power (watt) bulb is high.
  • Filament of electric bulb is of Tungsten.
  • Wire of electric heater is made of nichrome.
  • Fuse wire is made up of lead and tin.
  • Transformers work on the principle of electromagnetic induction.
  • A step-up transformer can convert low voltage, high frequency AC to high voltage, low frequency AC.
  • A step-low transformer converts high voltage, low frequency AC to low voltage, high frequency AC.
  • Transformer works on AC only.
  • Transformation ratio of step-up transformer is always greater than 1.
  • Ohm-meter is the unit of specific resistance.
  • Lead is used in storage battery.
  • Sliver is the best conductor of electricity.
  • Heating effect of current doesn’t depend upon the direction of current.
  • AC can’t be used in electroplating.
  • Soft iron is used in electric magnet.
  • Preventing formation of eddy currents, laminated cores are used in transformer.
  • Electric current is a continuous flow of electron.
  • Capacity of battery is shown in ’Ampere-hour’.
  • Chemical energy is stored in battery.
  • Specific resistance of any conductor depends upon material of conductor and temperature.
  • Dilute HCI is used in car battery.
  • AC is not suitable for charging of storage battery.
  • With increase in temperature there is decrease in resistance of Car­bon, Silicon and Platinum.
  • Muscovite is a common separator in electrical industries.
  • Dry cell is primary cell. Important physics notes by Pinnacle
  • Cadmium cell is called standard cell.
  • The frequency of AC mains in India is 50HZ.
  • The voltage difference of AC mains is 230V.
  • The resistance of Mercury is zero at 4K.
  • Copper is the most suitable for electric wire, because it has maximum number of free electrons.
  • Candalescent of tube-light is always greater than that of electric bulb of the same power

1 KW = 1.34 HP

    • Mica is a common insulator in electric industries.
    • Fluorine is often added to toothpaste in the form of fluoride ions.
    • Both fluorine and chlorine are added to water supplies for their germi­cidal properties.
    • Rhodium is the rarest metal.
    • Helium has the lowest boiling point of any element.
    • Osmium is the densest element.
    • Tungsten has the highest boiling point of all the elements. Hence, it is used for filaments in electric bulbs.
    • Cesium is used in atomic clocks.
    • Pure silicon is a semi-conductor and is used in electronic devices as the base for minute integrated circuits (ICs).
    • Mercury is the only metal which is liquid at room temperature. It is very poisonous and affects mental health.
    • 1 meter distance is equal to the length of 1,650,763.73 wavelength of pure orange lights emitted from Kr-86.
    • If a body is dropped vertically down, and another is projected horizon­tally then both will reach the ground simultaneously but with different velocity.
    • The ratio to distance traveled in 1st, 2nd, and 3rd seconds of freely falling body is 1:3:5.
    • The ratio of maximum height reached by different bodies projected up­wards with different velocity  is equal to
    • If a body is dropped from top of a tower of height h and another body is thrown up simultaneously with velocity u from the foot of the tower, then both of them would meet after time h/u.
    • Choke coil works on principle of electro-magnetic induction.

Physics Important notes

  • If a person projected a ball outside from a moving car, then the path of the ball is a straight line for the person sitting in the car, but It should be a parabola for an observer on the ground.
  • Retro-rocket is used for deceleration of rocket in space.
  • The shape of rain drop is spherical due to surface tension.
  • Goniometer is used in determining angle of
  • Lactometer is used to determining purity of milk.
  • The height of mercury column in barometer is independent of the di­ameter of glass-tube containing mercury.
  • The frequency of second pendulum is 2s.
  • Clouds are flying due to their least density and viscosity of air.
  • Viscosity of gases increases with increase in temperature.
  • The force of attraction between atoms of the same material is called cohesive force.
  • The force of attraction between atoms of different material is called adhesive force.

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