1. THERMIONIC EMISSION & RADIOACTIVITY

2. Bound electrons

3. Conduction electrons

4. Conduction electrons

5. Conduction electrons

6. Conduction electrons

7. Kinetic energy to e- provided by heating the metal - e- escapes
Thermionic emission

10. Edison’s experiment B A
Edison effect

11. Factors affecting rate of thermionic emission
Temperature of the surface:
t , rate of emission 
2. Nature of the metal surface:
 work function, rate of emission 
Surface area of the metal:
surface area , rate of emission 

12. Requisites of a good e- emitter
Work function: low
2. Melting point of the metal: high
Tungsten – melting point K
work function eV
Thoriated tungsten - work function – 2.6 eV
Tungsten coated with Ba/Cs/Sr - work function – 1 eV

13. Cathode Ray Tube

14. Cathode Ray Tube

15. Electron Gun

16. Electron Gun

17. Deflecting system

18. Deflecting system
Electrostatic deflection

19. Deflecting system
Electromagnetic deflection

20. Deflecting system
Electromagnetic deflection

21. Fluorescent screen

22. CRT in televisions

23. CRT in colour televisions