खनन और खनिज उद्योगों में पर्यावरणीय स्थिरता विषय पर विशेषज्ञों का मंथन पर्यावरणीय स्थिरता मानव समाज के निरन्तर अस्तित्व, समृद्धि और स्वास्थ्य के लिए मूलभूत शर्त है। हमारी न्यू जनरेशन को स्पीड और टेक्नोलॉजी पर ध्यान केंद्रित करना होगा ताकि भविष्य को सुनहरा बनाया जा सके। उक्त विचार मुख्य अतिथि श्री एमपी सिंह, प्रधान मुख्य अभियंता, केंद्रीय विद्युत प्राधिकरण विद्युत मंत्रालय भारत सरकार, नई दिल्ली ने व्यक्त किए श्री सिंह भूपाल नोबल्स स्नातकोत्तर महाविद्यालय में भूविज्ञान विभाग द्वारा "खनन और खनिज उद्योगों में पर्यावरणीय स्थिरता" विषय पर आयोजित दो दिवसीय राष्ट्रीय कॉन्फ्रेंस के समापन पर बोल रहे थे। दो दिवसीय राष्ट्रीय कान्फ्रेंस का भव्य समापन सम्मानित अतिथि प्रो विनोद अग्रवाल सदस्य, भारत सरकार नई दिल्ली स्थित MOEFCC की विशेषज्ञ मूल्यांकन समिति, (सि एण्ड टीपी) अपने उद्बोधन में कहा कि पर्यावरण स्थिरता सरकार और समाज दोनों की जिम्मेदारी है। वर्तमान में खनन उद्योग विभिन्न प्रावधानों एवं कानूनों के तहत कार्य कर रहा है ताकि पर्यावरण को सुरक्षित रखा जा सके। आयोजन सचिव डॉ. हेमंत सेन न...
Photo electric effect
Photo electric effect
- When light or E.M. radiation of suitable frequency or wavelength falls on a metal surface, it emits electrons.
- The process of emission of electrons from a metal surface, when illuminated by light of suitable wavelength or frequency is photoelectric effect.
- The electrons so emitted are photoelectrons.
Experimental Arrangement
- T = An evacuated glass tube with a quartz window W
- P = Photoelectrical sensitive plate
- C = Hollow cylinder which have a small hole to permit the incident light
- G = A sensitive galvanometer or ammeter
- P is connected with negative end of a battery with G
- C is connected with positive end of a battery
Working
- When light of suitable frequency falls on P from a source, the photoelectrons are emitted.
- Since collecting cathode C is connected to positive terminal of battery, so these electrons are attracted towards C.
- Thus photo electric current (IC) flows from P to C, and this current can be detected or measured by G.
- IC increases as the potential of C is more and more positive with respect to P.
Laws of photoelectric emission
- For every metal there is a particular frequency below which there is no photoelectric emission.
- The minimum frequency required for photoelectric emission is threshold frequency.
- As the intensity of incident light (IP) increases, IC also increases, i.e. IC ∝ IP.
- When the frequency of incident light is greater than threshold frequency.
- On increasing the positive potential of C, IC increases and it become maximum at a particular value of potential.
- A particular positive potential of collecting cathode C at which the photoelectric current is maximum, is known as saturated current.
- On increasing the negative potential of C, IC decreases and it become zero at a particular value of potential.
- The energy of the emitted photoelectrons is independent of intensity of incident light, and depends on the frequency of incident light and nature of the metal.
- Photoelectric emission is an instantaneous process.
Failure of the electromagnetic theory
- The calculation shows that the electron take 500 days to eject from sodium by using visible light of wavelength 4000Å, whereas experimentally there is no time delay.
- According to classical theory, light of greater intensity should impart large kinetic energy to the ejected electrons. But this does not happen.
- Classical theory shows that the velocity (energy) of the ejected electron should not depend on the frequency of the incident light, but in actual it depends.
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