Photoelectric effect

This slide about the famous Photoelectric Effect by one of the greatest scientist Albert Einstein
Photoelectric Effect
Elbert Einstein
Physics

1. TO OUR PRESENTATION 1

2. PRESENTATION TOPIC 2

3. PRESENTED By SHARIAR 191003049 BATCH 191(B) 3 NUSRAT 191003060

4.  When a beam of light of sufficiently high frequency onto a clean metal surface then the light will cause electrons to leave the surface.  Definition : the phenomenon of emission of electrons by the metals when they are exposed to light of suitable frequency is called as the photo electric effect and emitted electrons is called as photoelectrons . Photo electric effect 4

5. • A photon is absorbed by an electron in a metal surface causing an electron to be emitted. (E) Energy of photon = h*f Energy is conserved, “f” is the frequency , “h” planks constant h=6.626 × 10−34 js • Only electrons with energy above the work function energy will be emitted. • Only light with a frequency greater than the threshold frequency will cause emission • Energy=work function + Max KE of electron. E=h ν−Φ or K.E=h ν−Φ The Photoelectric Effect Equation 5

6. 6 The Photoelectric Effect Equation

7.  Threshold frequency is different for different material.  Photoelectric current is directly proportional to intensity of light.  The K.E. of photoelectrons is directly proportional to frequency of light.  Stopping potential is directly proportional to frequency.  The process is instantaneous. Characteristic of photoelectric effect 7

8. 8  In 1905, Einstein proposed that electromagnetic radiation or light is made up of photons. Thus the photon is the elementary element of light or light is made up of photons.  Einstein show that- light energy is not emitted continuously but it is emitted by individual amount of energy called as quantum of energy. PHOTON (QUANTUM OF LIGHT)

9. 9  According to Einstein, each photon of a light wave of frequency has the energy E is given by, E= h ν ………1  Where E= energy of photon(joule) h= planks constant-6.626 x 10-34 J.s ν= frequency of photon(Hz) Energy of photon

10. 10  A photon does not have any mass.  A photon does not have any charge and are not deflected in electric field or magnetic field.  All the quantum numbers are zero for a photon  In empty space, the photon moves at speed of light.  In the interaction of radiation with matter, radiation behaves as if it is made up of particles called photons.  The energy and momentum of a photon are related As follows E= p.c where p- magnitude of momentum and c is the speed of light.  Photon is called as a virtual particles. Properties of photon

11. 11 . The filter passes light of certain wavelengths from the lamp at left. The light strikes the curved electrode, and electrons are emitted. The adjustable voltage can be increased until the current stops flowing. This "stopping voltage" is a function only of the electrode material and the frequency of the incident light, and is not affected by the intensity of the light Schematic of experimental apparatus to demonstrate the photoelectric effect

12. 12  Principle : a photoelectric cell is a device which converts the light energy into an electrical energy.  Construction : it consists of an evacuated glass tube. Inside this tube photosensitive metal plate which is called emitter and a wire loop A which is acts as collector. Photo electric cell

13. 13  A high tension battery and micro ammeter (UA) are connected to plate C and loop A as shown in fig.  Working : When the light of suitable frequency is incident on the emitter C, it start emitted the photoelectrons are attracted towards the collector A. Working of photoelectric cell

14. 14  Construction : 1)the Hertz experimental set up used for studying the photoelectric effect is shown in above fig.  2) the set up consist of an evacuated glass tube that has a photosensitive metal plate C and another metal plate A as shown.  A monochromatic light source emerging from the source S of sufficiently short wavelength enters the glass window W and fall on photosensitive plate C, is called emitter. Photoelectric effect

15. 15  Working : when a beam of light fall on photosensitive metal plate c which is called emitter.  The plate c emits photoelectrons due to photoelectric effect. The photo electrons emitted by plate c will be attracted towards the positive plate A. these electron flows in the eternal ckt to cause an electric current in the ckt.  Such a current is known as the photoelectric current and measured by the micrometer connected in the ckts. Photoelectric effect

16. Applications & uses 16 Night vision devices Photons hitting a thin film of alkali metal or  semiconductor  material such as gallium arsenide in an  image intensifier  tube cause the ejection of photoelectrons due to the photoelectric effect

17. camera 17

18. 18 Solar cell Photoelectric effect also work for solar cell

19. 19 Burglar Alarm Photoelectric cell are also used for burglar alarm

20. 20 Light sensor Light sensor work by photoelectric effect

21. 21 1.  Photoelectric Effect  - Proved to us that light sometimes can act like a particle 2.  What's the Photoelectric Effect?   - When you shine light on certain metals they give off photoelectrons 3. What’s the function of photoelectric effect? - photons working in the theoretical prove 4. Uses of photoelectric effect - Shows different applications and real life uses . SUMMARY

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