Physics Education

Elastic limit  - The maximum stress which can be applied on a body without permanent deformation is called elastic limit. Hook's law - Within the elastic limit stress developed in a body is directly proportional to strain produced in it. Elastic constants & their relation Corresponding to three different types of stress & strain; there are three different modulus of elasticity. (i)  Young's Modulus (Y)  (ii)  Bulk Modulus (K) (iii)  Modulus of rigidity (η)  Young's Modulus (Y) Within the elastic limits, ratio of longitudinal stress to  longitudinal strain is called as  Young's Modulus denoted by "Y". Bulk Modulus (K) Within the elastic limits, ratio of volume stress to  volume  strain is called as  Bulk Modulus denoted by "K". Negative sign indicates that when pressure   increase volume decrease and vice versa. Compressibility Reciprocal of bulk modulus of elasticity is know...

Young's double slit experiment Young's in 1801 demonstrated the phenomenon of interference of light by a simple experiment. S is a narrow slit (of width 1 about 1 mm) lighted by a monochromatic (same color and wave length) source of light of at a suitable distance (about 10 cm)  from s, there are two fine slits S 1  & S 2  about 0.5 mm, parallel to S. when a screen is placed at a distance (about 2m) from the slits S 1  & S 2 ; alternate bright & dark fringes appear on the screen. The fringes disappear when one of the slits S 1  & S 2  is covered. click here to know basic of interference Explanation - Young's experiment can be explained on the basis of interference of light. According to Huygens principle, source of light "S" sends out spherical wave fronts. Let the solid arcs represent the crest & dotted arcs represent the troughs. These wave fronts reach the S 1  & S 2  click here to know about wavefron t ...

Spherometer A spherometer is an instrument for the precise measurement of the radius of curvature of a spherical surface. It consist of a base circle of three outer legs; & a center leg, which can be raised or lowered. 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 central leg touches the same surface as the other three legs are; & if zero of the circular scale does not coincide with the  zero of the  main scale then the instrument have zero error. It is of two types- (i)   Positive zero error= “0” of the circular scale lies below the "0” of the main scale. (ii)   Negative zero error= “0” of the circular scale lies above the "0” of the main scale. Total Reading(R)     Where L = the distance between the any two legs. h = height of curve surface from center leg. Formula for h = M.S.R + C.S.R x L.C C...

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...