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PRINCIPLE OF OPTICAL MEASURING INSTRUMENTS

PRINCIPLE OF OPTICAL MEASURING INSTRUMENTS. INTERFERENCE: When two wave trains of the same frequency & the same amplitude traveling in the same direction are superimposed on one another they produce interference

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PRINCIPLE OF OPTICAL MEASURING INSTRUMENTS

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  1. PRINCIPLE OF OPTICAL MEASURING INSTRUMENTS • INTERFERENCE: • When two wave trains of the same frequency & the same amplitude traveling in the same direction are superimposed on one another they produce interference • If at any point the waves are in phase, there is an increase in resultant amplitude, i.e. a constructive interference. • If the waves are out of phase & there is decrease in the resultant amplitude, i.e. destructive interference lec# 13 & 14

  2. PRINCIPLE OF OPTICAL MEASURING INSTRUMENTS 2. CONDITIONS FOR INTERFERENCE OF LIGHT WAVES: • The two sources should continuously emit waves of the same wave length or frequency • For obtaining interference fringes, the amplitude of the two interfering wave trains should equal or very nearly equal • The two sets of wave-trains from the two sources should either have the same phase or a constant in difference in phase • The two sources should be very narrow lec# 13 & 14

  3. PRINCIPLE OF OPTICAL MEASURING INSTRUMENTS 3. MONOCHROMATIC BEAM OF LIGHT: • A Monochromatic beam of light gives light of only one wave length or one color. • It is difficult to get a truly monochromatic source of light. However by using light filters it is possible to get a source that gives light within a narrow bend of wave lengths ±5x10-10m • Light emitted by certain elements eg. Mercury, sodium & cadmium is suitable. • In metrology this light is usually obtained from an electrical discharge lamp lec# 13 & 14

  4. PRINCIPLE OF OPTICAL MEASURING INSTRUMENTS • Depending upon the optical setup, the interference bands can appear as parallel bands, or as concentric circles • The interference phenomenon can be used to make the measurement of high precision by utilizing the fact that the path difference b/w two dark bands or two light bands is one wave length lec# 13 & 14

  5. PRACTICAL # 03 Object: To learn different uses of Combination set Apparatus: Combination set with 300mmblade, square head & centre head, sections for angle measurement Procedure: As Demonstrated Learning Outcome: After performing measurements with combination set we feel confidence to make its application independently lec# 13 & 14

  6. PRACTICAL # 03 Combination Sets can be used as: • Outside try square • Inside try square • Mitre Square • Sprit level • 45 level • Plumb level • Depth gauge • Height gauge • Marking gauge • Centre head use • Protractor use lec# 13 & 14

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