PHOTOELECTRIC EFFECT and it's principle.pptx

Photoelectric effect

1. PHOTO ELECTRIC EFFECT P RESENTED BY POONAM MSC PHYSICS

2. WHAT IS PHOTOELECTRIC EFFECT T HE PHENOMENON OF EJECTION OF ELECTRON FROM A METAL SURFACE WHEN ILLUMINATED BY LIGHT OR ANY OTHER RADIATION OF SUITABLE FREQUENCY IS CALLED PHOTOELECTRIC EFFECT . LIGHT ELECTRONS

3. DISCOVERY – YEAR – 1887 A GERMAN PHYSICIST IN CONNECTION TO WORK ON RADIO WAVES OBSERVED : WHEN ULTRAVIOLET LIGHT SHINES ON TWO METAL ELECTRODES WITH APPLY VOLTAGE THE LIGHT CHANGES THE VOLTAGE SPARKING TAKES PLACE BUT SPARK DECREASES WHEN APPARATUS WAS KEPT IN A DARK ROOM SIR HEINRICH RUDOLF HERTZ

4. EXPLAINATION – SIR ALBERT EINSTEIN GOT NOBLE –PRIZE FOR P.E EFFECT IN 1921 YEAR ----1905 SIR ALBERT EINSTEIN EXPLAINED THE PHOTOTELECTRIC EFFECT BY TERMS : PHOTONS THRESHOLD ENERGY THRESHOLD FREQUENCY WORK FUNCTION EFFECT OF INTENSITY OF LIGHT ENERGY OF PHOTON = WORK FUNCTION + KINETIC ENERGY

5. EXPERIMENTAL SETUP :- SOURCE OF RADIATION SIMPLE QUARTZ TUBE PHOTO SENSITIVE EMITTER PLATE COLLECTOR PLATE A HIGH TENSION BATTERY A MICRO AMMETER TO MEASURE THE CURRENT

6. RESULTS:- EFFECT OF INTENSITY OF LIGHT ON PHOTOELECTRIC CURRENT : EFFECT OF POTENTIAL ON PHOTOELECTRIC CURRENT :

7. EFFECT OF FREQUENCY OF INCIDENT RADIATIONS ON PHOTOELECTRIC CURRENT THRESHOLD FREQUENCY

8. LAWS OF PHOTOELECTRIC EMISSION : FOR A GIVEN METAL AND FREQUENCY OF INCIDENT RADIATION NUMBER OF PHOTOELECTRONS INTENSITY OF THE EMITTED PER SECOND INCIDENT LIGHT FOR EVERY METAL THERE EXISTS A MINIMUM FREQUENCY OF INCIDENT RADIATION BELOW WHICH NO EMISSION TAKES PLACE CALLED THRESHOLD FREQUENCY ABOVE THRESHOLD FREQUENCY, THE REST ENERGY OF PHOTON CONVERTED INTO THE KINWTIC ENERGY OF THE ELECTRON. IT DEPENDS ON THE FREQUENCY OF THE INCIDENT RADAIATION. PHOTOELECTRIC EMISSION IS AN INSTANTANOUS PROCESS.THE TIME LAG BETWEEN THE INCIDENCE OF RADIATION AND EMISSION OF THE ELECTROM IS VERY SMALL ,ABOUT LESS THAN 10*-9 SECONDS.

9. PHOTOELECTRIC CELL:- THE DEVICE WHICH CONVERTS LIGHT ENERGY ELECTRICAL ENERGY PHOTOELECTRIC CELL ARE OF TREE TYPES:- 1) PHOTOEMISSIVE CELL 2) PHOTOVOLTIC CELL 3)PHOTOCONDUCTIVE CELL

10. APPLICATIONS OF PHOTOELECTRIC CELL 1) AUTOMATIC CAMERAS:- CAMERA HAS A BUILT IN LIGHT METER LIGHT ENTERING INTO THE LIGHT METER STRIKES THE METAL OBJECT;ELECTRONS ARE RELEASED AND CURRENT CREATED THIS AUTOMATICALLY OPENS AND CLOSES THE LENS TO ADJUST FOR HIGH AND LOW LIGHTENING CONDITIONS.

11. 2) AUTOMATIC OPERATION OF GARAGE DOOR:- 1) SOURCE OF LIGHT IS FITTED ON ONE SIDE AND BATTERY OPERATED PHOTOCELL CONNECTED TO MECHANICAL ARRANGEMENT FIXED ON THE OTHER SIDE OF DOOR. 2) THE DOOR OPENS OR CLOSES WHWNEVER THE LIGHT FALLING FROM THE PHOTOCELL IS OBSTRUCTED.

12. OTHER APPLICATIONS :- 1) BURGLAR ALARM 2)SMOKE DETECTOR 3)FIRE ALARMS 4)COUNTING DEVICES 5) IN INDUSTRIES FOR LOCATING MINOR FLAWS OR HOLES IN METALLIC SHEETS

13. QUERIES ?

14. THANK YOU ALL