Physics Education

Huygens wave theory This theory tells us as to how new waves are formed & how they propagate. Light travel in form of longitudinal waves, with uniform velocity in homogeneous medium. Different colors are due to different wavelengths. When wave enter our eye & gives energy we have sensation of light. The waves are formed in a hypothetical medium "ether" which is present everywhere in universe Success – It could explain Interference, diffraction, Reflection & Refraction.     It predicts that in denser medium its wave length will be decreased hence velocity will decrease. Experiments proved it. (Supported it) Failure- It could not explain polarization, Compton effect, photo electric effect. And light is transverse. Existence of ether could not be proved as there are no traces of drag by Michelson Morley experiment. Energy of wave does not depend on its amplitude but depends on frequency. Color doe...

Newton's corpuscles theory 1) Every source of light emits large number of tiny particles known as corpuscles in a                medium surrounding the source.    2) The tiny particles travel with high velocity, perfectly elastic, & having negligible mass. 3) The corpuscles would travel faster in the denser medium than in rarer medium. 4). When the corpuscles hit our retina in the eye, we get a sensation called light. 5). Different colors of light are due to different size of corpuscles. Corpuscles theory could not explains 1) Reflection & refraction on the surface of liquid. 2) Could not explain about Interference, diffraction & Polarization. 3) Speed of light in denser medium as per corpuscular - theory should increase, but in              practice found to be decrease. 4) The mass of source must decrease after long emission but i...

Dispersion of light It is the phenomenon of splitting of a beam of white light into its constituent colors on passing through a prism. The band of seven colors so obtain is called the spectrum .  Cause of dispersion is each color has its own characteristics Wavelength (λ). The order of colors from lower end of the spectrum is Violet(V), Indigo(I), Blue (B), Green(G), Yellow (Y), Orange (O), & Red (R); & can be recollected by the word VIRGYOR. In the above figure violet color is deviates from maximum angle & Red color deviates from minimum angle. Dispersion is denoted by ઠ(Delta). ઠ = ( μ−1)A where μ= Refractive Index of Prism’s medium            A= Angle of Prism. Angle of Dispersion : Angle of Dispersion = ઠ V - ઠ R                                      Angle of Dispersion   = ( μ V...

Least count   smallest possible measuring that can be measured accurately using given instrument is called least count of instrument. method to find least count of simple scale- Range of instrument Range is minimum to maximum possible measurement of a given instrument. In fig above                Range = 0.1 cm to 15 cm (for example-i) Similarly Range = 0.0625 inch to 6 inch (for example-ii)  Vernier Caliper   It is the instrument used for measuring length, internal-external diameter, depth, thickness & height of a tube or tube like structure. It consist of a main scale & vernier scale. Invented by Pierre Vernier in 1631. Using a simple scale we can accurately measure up-to one digit of decimal but using vernier caliper we can measure accurately up-to second digit of decimal.  Least count of vernier scale L.C = 1 M.S.D - 1 V.S.D where M.S.D - main scale division       ...

Micrometer Screw gauge It is the instrument used for precise measurement of quantities such as length, diameter and thickness. It consist of two scales a main scale & circular scale. Pitch : - It is the distance between two consecutive threads of a screw or It is the distance moved in one rotation by screw. Zero error - When the screw of the micrometer completely touches the fixed stud; the zero of the circular scale does not coincide with the reference line then instrument have zero error. It is of two types – (i) positive error      (ii) negative error Correction of  error   Steps             1. Count the number of division beyond the reference line.            2. multiply step 1 with L.C          3. For positive error subtract the data of step 2 with total reading & f or negative error add the...

Accuracy & Precision Accuracy -  Accuracy refers to the closeness of a reading from true value; taken by a measuring instrument. Precision - Precision refers to the closeness of two or more readings taken by a measuring instrument. The above two statement will get a clear view from the following example- let the true value of tea in a cup is 20 ml.   Difference between accuracy and precision Accuracy Precision Accuracy is the agreement of the result of measurement with true value. It is an ability to approach correct result. Repeatability of measuring process is called Precision Your measurement will be close to the standard measurement. Your measurement will be similar every time you measure. Accuracy can be improved. Precision cannot be improved. Accuracy depends upon simple techniques of analysis. Precision depends upon many factors like tempe...

Unit & Measurement Measurement -  It is a process of finding an unknown quantity with the standard reference one. Need of measurements   If all the quantities measured are clearly defined then there is no chance of confusion between two persons. The aim of measurement is determined whether the product is manufactured as per the requirement. To identify various law. Measurement plays a key role in development of engineering & science. To assure the quality of the product. Physical quantity -  A characteristics(property) which can be measured & which follows laws of physics is called a physical quantity. E.g. - Mass, length, Time, velocity, acceleration etc. Types of physical quantity- (i) Fundamental or base quantity - The physical quantity which do not depend on the other physical quantity are known as fundamental or Base quantity. There are 7 fundamental quantities a) Mass           ...