Upcoming SlideShare
×

# Energy Levels And Spectra

2,263 views

Published on

Published in: Technology
2 Likes
Statistics
Notes
• Full Name
Comment goes here.

Are you sure you want to Yes No
• Be the first to comment

Views
Total views
2,263
On SlideShare
0
From Embeds
0
Number of Embeds
21
Actions
Shares
0
0
0
Likes
2
Embeds 0
No embeds

No notes for slide

### Energy Levels And Spectra

1. 1. How Do Electrons in Atoms absorb Energy? Quantum Behaviour
2. 2. Energy Levels and Spectra <ul><li>We will find out: </li></ul><ul><ul><li>How electrons in atoms absorb energy from photons </li></ul></ul><ul><ul><li>How spectra tell us the type of atom present </li></ul></ul>
3. 4. v v v v v E2 E1 The Electron Goes from Energy Level E1 to E2 Energy Absorbed = hf = E2 – E1
4. 5. v v v v v v Energy of Emitted photon = hf = E2 – E1 E2 E1
5. 6. Absorption Spectra These lines show where particular wavelengths (frequencies) have been absorbed. They are emitted in all direction so are not added back in.
6. 7. Examples <ul><li>A photon is absorbed by an atom and an electron is excited from energy level -13eV to -8eV. What is the frequency of the photon? Wavelength? </li></ul><ul><li>E2 – E1 = hf </li></ul><ul><li>E2 – E1 = (-8) – (- 13) = 5eV = 5 x 1.6 x 10 -19 Joules </li></ul><ul><li>= 8 x 10 -19 Joules = hf </li></ul><ul><li>Therefore f = 8 x 10 -19 / 6.6 x 10 -34 = 1.2 x 10 15 Hz </li></ul><ul><li>As c = f x  therefore  = c / f = 3 x 10 8 / 1.2 x 10 15 </li></ul>
7. 8. Phasors <ul><li>Phasors represent waves in terms of: </li></ul><ul><ul><li>Amplitude – Length </li></ul></ul><ul><ul><li>Frequency – Number of turns on 1 second </li></ul></ul>But a photon also has frequency but the magnitude is arbitrary in this case
8. 9. Phasors and Interference <ul><li>When more than one phasor interact, they interfere. </li></ul><ul><li>We add them ‘tip-to-tail’ to see the outcome – constructive or destructive interference </li></ul>In Phase – Phasors Add  /2 out of phase Out of Phase – Phasors Cancel Resultant The phasor magnitude is normally 1
9. 10. Phasors <ul><li>But how do we know the phase of a phasor at any one time..? </li></ul><ul><li>It depends on the path! </li></ul><ul><li>But how does the phasor know which path to take..? </li></ul>
10. 11. Calculating Phase Position <ul><li>Phasors leave a source in phase – i.e. lined up </li></ul><ul><li>To calculate their relative phase at a time and path length we use: </li></ul><ul><li>Trip Time = Distance / Speed </li></ul><ul><li>Speed = f x  = c where c = speed of light = 3 x 10 8 m/s </li></ul><ul><li>Number of Rotations = Rotations per second x Number of seconds </li></ul>This is frequency
11. 12. Question 10s <ul><li>Complete the questions using the 3 equations </li></ul><ul><li>Trip Time = Distance / Speed </li></ul><ul><li>Speed = f x  = c where c = speed of light = 3 x 10 8 m/s </li></ul><ul><li>Number of Rotations = Rotations per second x Number of seconds </li></ul>