Elecric Field
Frictional Electricity: Frictional electricity is the electricity caused due to friction. When two neutral bodies (e.g. glass rod and silk) are rubbed together, both gets charged and the charges produced on them are opposite in nature. The reason of both bodies being electrified is that some of electrons of one body are transferred to the other. Types of charges: Charges are of two types: (i) Positive charges (ii) Negative charges Electrons possess negative charge. Therefore when a body gains electrons, it becomes negatively charged but when...
read moreDoppler’s effect
Doppler’s Effect: The apparent change in frequency of a sounding body due to relative motion between source and observer is called Doppler’s effect. Doppler’s effect takes place both in sound and light. In sound it depends on whether the source or observer or both are in motion; while in light it depends only on the fact that whether the distance between source and observer is decreasing or increasing. Doppler’s Effect in Sound (i) Source in motion and observer at rest. If source is approaching the observer with speed vs, then n...
read morePrinciple of superposition
Principle of superposition When two or more waves propagating in a medium arrive at the same point simultaneously, a new wave is produced. This phenomenon is called superposition of According to Young the net displacement at any point of the medium is equal to the algebraic sum of displacements of individual waves arriving at that point simultaneously. This is called the principle of superposition and holds good as long as the amplitude of the waves is not too large. This principle is of extreme importance and can be applied to many types of...
read moreWave motion
Wave motion: Wave: Wave is defined as the continuous transfer of state from one part of the medium to the other with finite velocity without changing its form. There are two types of waves : (i) Mechanical waves: The waves which require a material medium for their propagation are called mechanical waves. Sound waves in air, waves in stretched string are examples of mechanical waves. (ii) Electromagnetic waves: The waves which require no material medium for their propagation are called electromagnetic waves. The examples of electromagnetic...
read moreAlternating Current and Electrical Devices
Alternating Current An alternating current is one which changes in magnitude and direction periodically and is abbreviated as a.c. The source of alternating emf may be a dyamo or an electronic oscillator. The alternating emf E at any instant may be expressed as: Where is angular frequency of alternating emf and is the peak value or amplitude of alternating emf. The frequency of alternating emf, And time period of alternating emf, The alternating current in a circuit, fed by an alternating...
read moreNuclei
Composition of Nucleus The atom consists of central nucleus, containing entire positive charge and almost entire mass. According to accepted model the nucleus is composed of protons and neutrons. The proton was discovered by Rutherford by bombardment of -particles on nitrogen in accordance with the following equation : The superscripts (on the right) denote the mass number and subscripts (on the left) denote the atomic number. The neutron was discovered by Chadwick by the bombardment of -particles on beryllium in accordance...
read moreReflection, Refraction and Total Internal Reflection
Ray optics as a limiting case of wave optics In my optics (also called geometrical optics) the light is supposed to be propagating in straight lines, called the light rays, which are supposed to be formed of corpuscles. In wave optics light is supposed to be propagating in the form of waves. The phenomena of interference, diffraction and polarization could only be explained by wave theory. The diffraction of light is the bending of light round the edges of the obstacle, due to which sharp images of the objects may not be seen. The...
read moreDispersion, Spectra and Optical instrument
Refraction through a Prism A prism is a transparent medium enclosed by two plane refracting surfaces. Let EF be the monochromatic ray incident on the face PQ of prism PQR of refracting angle A at angle of incidence . The ray is refracted along FG, ; being angle of refraction. The ray FG is incident on the face PR at angle of incidence and is refracted in air along GH. Thus GH is the emergent ray and is the angle of emergence. The angle between incident ray EF and emergent ray GH is called angle of deviation ...
read moreAtoms and Molecules
Thomson Empirical Atom-Model According to this model the mass and positive charge of an atom his uniformly distributed over the entire volume of atom and the electrons are embedded in this uniform distribution. This model is called the plumpudding model. The model could explain the stability and neutrality of atom; but could not explain the discrete emission of radiations and the large angle scattering of -particles by the foil. As the model was empirical and had no experimental basis, therefore, it was...
read moreElectrons and Photons
Cathode Ray Cathode rays are the streams of electrons and were discovered by Sir William Crooke. They are produced by: (i) A discharge tube containing gas at allow pressure of the order mm of Hg. At this pressure the gas molecules ionize and the emitted electrons travel towards positive potential of anode. The positive ions hit the cathode to cause emission of electrons from cathode. These electrons also move towards anode. Thus the cathode rays in the discharge tube are the electrons produced due to ionization of gas and that emitted...
read more