Physics Important notes for SSC CGL / CHSL exam : GK

Physics Important notes for SSC CGL / CHSL exam : GK

FACTS TO REMEMBER : Important

• 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.
• 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.

• 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.