Post on 07-Jan-2016
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Chemical Ideas 6.7
Where does colour come from?
25 questions to see what you’ve
remembered.
More about the colour we see .. Key stage 3 stuff.
1. What colour is the light reaching my eye? Explain.
Red filter
transmit absorb reflect
2. What colour is the light reaching my eye? Explain.
Blue filter
transmit absorb reflect
3. What colour is the light reaching my eye? Explain.
Colourless glass
transmit absorb reflect
4. What colour does the ball
look? Explain.
transmit absorb reflect
5. What colour does the ball
look? Explain.
transmit absorb reflect
6. What colour does the ball
look? Explain.
transmit absorb reflect
7. What colour does the ball look? Explain
transmit absorb reflect
8. What colour does the ball
look? Explain.
transmit absorb reflect
9. The rays are …
•A. Refracted
•B. Reflected
•C. Dispersed
•D. Converged
10. Name the 3 primary colours of light …
Chemical Ideas 6.1
Light and the electron.
Sometimes we use the wave model for light …
• λ (lambda)= wavelength
11. Wavelength increases, Frequency ?
C
•12. Sketch the e.m.s. and use arrows to
mark:
•Increasing energy•Increasing wavelength•Increasing frequency
C = λν problems….
Work out v:
13. If λ is 3.00 m
14 If λ is 30.0 cm
15. If λ is 3.00 mm
Work out λ:
16. If ν is 3.00 x 1010 Hz
c = 3.00x108 m s-1
Sometimes we use the particle model …hE
• Packages of energy are called photons
• Light is a stream of photons
• E = 6.63 x10-34 x 4.5 x 1014 = 3.0 x 10-19 J
14105.4 x Hz
h = 6.63 x 10-34 J Hz -1
Planck constant
E = hν problems …
• h = 6.63 x 10-34 J Hz -1
• Planck constant
17. If the frequency is 1.089 x 106 Hz, what is the energy of each photon?
18. If E = 3.65 x 10-20 J per photon, what is the frequency (ν) of the radiation?
19. Absorption or emission Spectrum of hydrogen?
• Black background
• Coloured lines.
Spectroscopy• Sample of
hydrogen
• High voltage
• Prism
• Electrons can only exist in fixed energy levels.
ΔE
h
E
• Electrons absorb energy and move to a higher energy level.
• The electrons drop back to a lower energy level and emit energy.
• The frequency of the radiation emitted depends on ΔE.
20. Red? 21. Blue/green?
?
5
7 etc
1
2
34
6
22. Why no
• 7 2
• 8 2
• 9 2?
23. What happens to electrons?
1
234
Chemical Ideas 6.2What happens when
radiation interacts with matter?
Molecules are made of more than one atom but they still have
electrons.• Electronic
transitions
Vis + UV
24. Molecules move ! How?
25.There are vibrational energy levels as well as electronic energy level . ΔE in which
region?
The answers …
1. What colour is the light reaching my eye? Explain.
Red filter
Red
2. What colour is the light reaching my eye? Explain.
Blue filter
Blue
3. What colour is the light reaching my eye? Explain.
Colourless glass White
4. What colour does the ball
look? Explain.
Red
5. What colour does the ball
look? Explain.
Black
6. What colour does the ball
look? Explain.
White
7.What colour does the ball
look? Explain.Red
8. What colour does the ball
look? Explain.Black
9. The rays are …
•A. Refracted
•B. Reflected
•C. Dispersed
•D. Converged
10. Name the 3 primary colours of light …
Sometimes we use the wave model for light …
• λ (lambda)= wavelength
11. Wavelength increases, Frequency ?
C
decreases
energy
wavelength
frequency
12.
c = λ ν
υcλ
c
c
νλ
c = speed of light = 3.00 x 108 m s-1
λ = wavelength m lambda
ν = frequency Hz ( or s-1 ) nu
c
Use m
for λ
C = λν problems….
Work out v:
13. If λ is 3.00 m
14. If λ is 30.0 cm
15. If λ is 3.00 mm
Work out λ:
16. If ν is 3.00 x 1010 Hz
c = 3.00x108 m s-1
Sometimes we use the particle model …hE
• Packages of energy are called photons
• Light is a stream of photons
• E = 6.63 x10-34 x 4.5 x 1014 = 3.0 x 10-19 J
14105.4 x Hz
h = 6.63 x 10-34 J Hz -1
Planck constant
Rearranging again….
hE
h
E
E
h
E = hν problems …
• h = 6.63 x 10-34 J Hz -1
• Planck constant
17. If the frequency is 1.089 x 106 Hz, what is the energy of each photon?
18. If E = 3.65 x 10-20 J per photon, what is the frequency (ν) of the radiation?
19.
• Black background
• Coloured lines.
emission
Spectroscopy• Sample of
hydrogen
• High voltage
• Prism
• Electrons can only exist in fixed energy levels.
ΔE
h
E
• Electrons absorb energy and move to a higher energy level.
• The electrons drop back to a lower energy level and emit energy.
• The frequency of the radiation emitted depends on ΔE.
20. 3 2 21. 4 2
?
5
7 etc
1
2
34
6
22. Why no
• 7 2
• 8 2
• 9 2?
visible ultra violet
E increases
6
1
234
Balmer 2
E increasing
Lyman ?
1
234
1
Absorption Spectrum of hydrogen.
• Continuous spectrum
• Black lines.
How do the 2 compare?
23.What happens to electrons?
1
234
• Electrons absorb energy
• Electrons are excited
• Electrons move to higher energy level
• E = h v
Molecules are made of more than one atom but they still have
electrons.• Electronic
transitions
Vis + UV
24. Molecules move ! How?
25. There are vibrational energy levels as well as electronic
energy level ..
I.R.
• Electronic transitions
Vis + UV
• Rotational transitions
• Vibrational transitions
Microwave
I.R.
Chemical Ideas 6.7
Where does colour come from?
•Absorb
•Transmits
•Complementary
•Absorb
•Transmits
•Complementary
•Absorb
•Transmits
•Complementary
X2
X2*
e-
e-
filter
meter
photocell
cuvette
concentration
absorbance Absorbance α concentration