Photo Electric Effect

Photoelectric Effect :It is the emission of photo electron from the surface of metal when a light of certain minimum frequency falls over it.

Properties of photoelectric effect :

• The energy required to just take out electron from the metal surface is called work function (Wo).
• The minimum frequency of light below which the photoelectric effect does not takes place is called THRESHOLD FREQUENCY.
• Number of photo electron depends on the brightness  or intensity of light striking on the metal surface. Brighter the light greater the number of photo electron emitted.
• As soon as the beam of light strikes the metal surface, photo electrons emitted by the metal surface. It means there is no time gap between striking of light and emission of photo electron.
• The energy of beam of light striking on metal surface is divided into two parts one for the emission of electron (work function) and the remaining as the kinetic energy of the photo electron.

                   Energy = work function + kinetic energy

                           hν = hν₀ + 1/2 mv2        

  { hν= energy of light source,  hν₀ = work function, 1/2 mv2  = kinetic energy of photo electron}

                        hν = W₀ + 1/2 mv2

                        1/2 mv2  = (hν - hν₀)

                        kinetic energy = h(ν - ν₀)

 {m= mass of electron, h=plank’s constant(6.62 X 10-34 ), ν=frequency of light, ν₀= threshold frequency}

               W₀ = hν₀            (where, ν₀ = c/λ₀)

                         

                                                                   https://youtu.be/UCHIvvAvekA

Electromagnetic Wave

Electromagnetic waves :  The wave which are produced when a particle is accelerated due to varying electric and magnetic field. EMW consist both electric and magnetic field perpendicular to each other as well as perpendicular to the direction of propagation of wave.

Properties of Electromagnetic waves are ---

• They do not require any medium to travel.
• When these waves are arranged from low wavelength to high wavelength region, then they forms a spectrum known as EM spectrum.
• Gamma waves are the lowest wavelength wave and radio waves are the highest wavelength wave of EM spectrum.
• EM waves shows all the characteristics of wave like frequency, amplitude, wavelength etc.
• These waves follows the relation ---

                                      f = 1/T                             and

                                      c = f入             

                {c=speed of light, f=frequency, 入=wavelength }

       

                                        

                                                                                https://youtu.be/UCHIvvAvekA

Dalton's Atomic Theory

Dalton's Atomic Theory :The postulates of this theory are -----

• An atom is the smallest individual particle of matter.
• In a chemical reaction, an atom can neither be created nor be destroyed but they are re-organised.
• Atoms of different elements combine in fixed ratio to form a compound.
• Atom of same elements shows similar property and atoms of different elements shows different property.

                                                                                        https://youtu.be/UCHIvvAvekA

Frame of reference

Frame of Reference :The co-ordinate system relative to which the position and motion of an object can be described is called Frame of Reference.

Type of Frame of Reference :

1) Inertial Frame of Reference :The frame of reference in which Newton's law of inertia is valid.

exam:- The frame of reference at rest or the frame moving with constant velocity are inertial frame of reference.

2) Non-Inertial Frame of Reference : The frame of reference in which the Newton's law of inertia is not Valid is called non-inertial frame of reference.

exam:- The accelerated frames or the rotating frames are non-inertial frame of reference. 

                                                                                          https://youtu.be/UCHIvvAvekA

Buoyancy

BUOYANCY :When an object is immersed in a liquid, it exerts an upward force on the object, this phenomenon of upward movement is called Buoyancy.

The upward force exerted by the liquid on the object immersed in it, is called upthrust or buoyant force. The magnitude of buoyant force depends on the density  of the liquid.

• If the buoyant force applied by a liquid on an object is greater than the weight of the object, then the object will float in that liquid.
• If the buoyant force is less than the weight of the object will sink in that liquid.
• The magnitude of buoyant force depends on the density.

                                                                                            https://youtu.be/UCHIvvAvekA

Herbaria

Herbaria :Herbaria is a place where dried and pressed plants specimens, mounted on sheets are kept systematically according to a widely accepted system of classification. Herbarium is a repository or store house for future use.

• It provide information about the local flora as well as flora of distant area.
• It provides information about the ecology of different places. The information is useful in locating wild varieties and relatives of economically important plants.
• It serves as a quick referal system for taxonomic studies.
• Largest herbarium of the world is at kew.

                               

                                                                                   https://youtu.be/UCHIvvAvekA

Cyanobacteria

Cyanobacteria :Cyanobacteria or blue-green algae are gram(+ve) photosynthetic prokaryotes known to be the earliest colonisers of barren area because of their ability to perform oxygenic photosynthesis. Cyanobacteria contains chlorophyll a, carotenoids and phycobilins as photosynthetic pigments.

Food is stored in the form of cyanophycean starch, lipid globules and protein granules. 

They have evolved more than 3 billion years back, added oxygen to the atmosphere and paved the path for evolution of aerobic forms, including aerobic bacteria.

                                                                             https://youtu.be/UCHIvvAvekA