1. REVISION PHOTOELECTRIC EFFECT

2. the process whereby electrons are ejected from a metal surface when light of suitable frequency is incident on that surface.. IT PROVES... the particle nature of light

3. THRESHOLD FREQUENCY f o, as the minimum frequency of light needed to emit electrons from a certain metal surface. WORK FUNCTION W o, the minimum energy that an electron in the metal needs to be emitted from the metal surface

4. Different metals have different work functions, because they have different ionization energies Ionization energy is the energy required to remove valence electrons from outer orbitals

5. 3 SCENARIOS Photo electrons are emitted Photo electrons are emitted and move away using kinetic energy Photo electrons are NOT emitted

8. INTENSITY & FREQUENCY http://phet.colorado.edu/en/simulation/photoelectric EXPERIMENT

9. INTENSITY & FREQUENCY To increase the CURRENT the rate of flow of current must be increased

10. FREQUENCY Frequency depends on the wavelength of light. Frequency influences the amount of energy of the photons. To increase the CURRENT The photons require more energy in order to increase the electrons kinetic energy Therefore we INCREASE the FREQUENCY (or DECREASE the WAVELENGTH)

11. INTENSITY Intensity depends on the number of light sources Intensity influences the number of photons that are released To increase the CURRENT More electrons need to be release per time Which means that more photons need to reach the surface Therefore we INCREASE the INTENSITY

12. Increasing the INTENSITY does NOT change the kinetic energy of the photo-electrons (because the energy of the photons didn’t change) So if there AREN’T any photo-electrons released at a specific frequency, it will not help to increase the intensity, because the photons will still lack sufficient energy To change the speed of the photo-electrons, the frequency (energy) of the photons needs to change

13. ABSORPTION & EMISSION SPECTRA

14. An atomic absorption spectrum is formed when certain frequencies of electromagnetic radiation that passes through a medium, e.g. a cold gas, is absorbed An atomic emission spectrum is formed when certain frequencies of electromagnetic radiation are emitted due to an atom's electrons making a transition from a high-energy state to a lower energy state.

15. HYDROGEN

16. ABSORPTION vs EMISSION