1 / 30

Intensity

Intensity. I. (W m - 2 ). Intensity = Power. Area. P. I =. A. Inverse square law. I d 2 =. I d 2. A A. B B. Photoelectric effect. current. f o. frequency. Energy of photons. E = h f. h is Planck’s constant. Intensity of photons. I = N h f.

mai
Download Presentation

Intensity

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Intensity I (W m-2)

  2. Intensity = Power Area P I = A

  3. Inverse square law I d2= I d2 A A B B

  4. Photoelectric effect current fo frequency

  5. Energy of photons E = h f h is Planck’s constant

  6. Intensity of photons I = N h f N is number of photons per second

  7. Work function Minimum energy to release electron from a surface (E = h fo)

  8. Kinetic Energy E = h f - h fo Energy above minimum appears as kinetic

  9. Emission spectra W2 red W1 violet W0

  10. Emission spectra W2 – W1 = h f Electron ‘jumps’ from excited level to lower level

  11. Emission spectra Bright emission lines - more electrons

  12. Absorption spectra W2 Photon ofenergyh f W1

  13. Absorption spectra W2 = W1+ h f Electron absorbs radiation and ‘jumps’ to excited level

  14. Spontaneous emission random process

  15. Stimulated emission Photon (energy h f) can cause atom to emit photon (energy h f) in phase and same direction

  16. Laser E1 Stimulating photon (hf) E0

  17. Laser Monochromatic Coherent Intense

  18. Semiconductors n-type p-type

  19. n-type Conduction by negative electrons

  20. p-type Conduction by ‘positive’ holes

  21. Forward-biased n-type p-type electrons diode conducts

  22. Reverse-biased n-type p-type diode does not conduct

  23. Diode Forward-biased diode electron and hole recombine Photon (heat) emitted

  24. LED Forward-biased diode electron and hole recombine Photon (light) emitted

  25. photodiode Photovoltaic mode supplies power e.g. solar cell

  26. photodiode Photoconductive mode (reverse bias) light sensor

  27. MOSFET n-region implant drain oxide layer n-channel gate p-type substrate source n-channel enhancement MOSFET

  28. MOSFET Can switch on a load. Apply gate voltage VGS to turn ‘on’ MOSFET

  29. MOSFET + V load D Io G S VGS 0 V n-channel enhancement MOSFET

  30. MOSFET Can also be used as an AMPLIFIER

More Related