1. Lecture 6 Light and matter Harris Ch.18.

2. Light striking a sample can be 1. reflected 2. transmitted 3. absorbed 4. scattered

3. Reflected light Incident light Emergent light P0P0 P1P1 Absorbed light Scattered light

4. Refractive index

5. Air Glass Longer wavelength Shorter wavelength   Snell’s law

6. Reflected light P r Incident lightEmergent light P0P0

7. Incident lightEmergent light Transparent plate P0P0 P1P1

8. Air 1 Quarz 1.5 Water 1.33 T=0.85 R=0.04 Air-quarz Water-quarz R=0.003 T=0.92 emptyWith water

9. Absorbing plate

10. Incident light Emergent light Absorbing plate P0P0 P1P1 0 l dx dP P dP= N   P N=C  Volume Volume= 1  dx N = C  dx

11. Incident light Emergent light Absorbing plate P0P0 P1P1 0 l dx dP P

12. Incident light Emergent light Absorbing plate P0P0 P1P1 0 l dx dP P absorbance Sensitivity is the same for any power (P)

13. Beer’s law Bugert, Lambert and Beer A concentration Straight line!

14. When photon is absorbed, the system jumps to the next energy level

15. Luminescence A photon is absorbed and then re-emitted at different wavelength

16. Incident light P0P0 Emergent light P1P1 Re-emitted light Absorbed light

17. If absorbance is small:

18. Incident light P0P0 Emergent light P1P1 Re-emitted light Absorbed light sensetivity is proportional to the source power

19. Limits to Beer’s Law Polychromatic light (several wavelength)

20. Limits to Beer’s Law Incident light P0P0 Emergent light P1P1 Stray light