1. In Voltaire’s “Elémens de la Theorie de Newton“ (1738)

2. Fraunhofer Absorption Lines in the Sun’s Spectrum
Na D lines Orange street lamps contain sodium

3. Emission Spectra from Nebulae

5. Photon from local star

6. photoionisation

7. recombination

11. Energy Levels
E(n) = - R/n2

12. Energy Levels
E(n) = - R/n2
F(n) = - R/n2 (in cm-1)

13. Energy Levels
E(n) = - R/n2
F(n) = - R/n2 (in cm-1)
R = cm-1

14. Energy Levels
E(n) = - R/n2
F(n) = - R/n2 (in cm-1)
R = cm-1
For n=  emission lines

15. Energy Levels
E(n) = - R/n2
F(n) = - R/n2 (in cm-1)
R = cm-1
For n=  emission lines
n2 = n+1
n1 = n

16. Energy Levels
E(n) = - R/n2
F(n) = - R/n2 (in cm-1)
R = cm-1
For n=  emission lines
n2 = n+1
n1 = n
Transition Frequencies
F(n1) = - R[ 1/n22 – 1/n12]

18. Bohr radius

19. Bohr radius
an = a1n2

20. Bohr radius
an = a1n2
a1 ~ 0.5 Å

21. Bohr radius
an = a1n2
a1 ~ 0.5 Å a1 = Å

22. Bohr radius
an = a1n2
a1 ~ 0.5 Å a1 = Å (Å = 10-8 cm)

23. a2 ~ 0.5 x4 Å = 2 Å

24. a3 ~ 0.5 x 9 Å = 4.5 Å

25. a3 ~ 0.5 x 16 Å = 8 Å