1. Chapter 5.3 Light, Wavelength and the Atomic Spectrum
Chapter 5.3 Light, Wavelength and the Atomic Spectrum

2. I. Light
When a sample absorbs visible light the color we see is the sum of the remaining colors that are __________ or ___________ by the object.
reflected
transmitted
light
An opaque object reflects _________ and a clear object ________ light.
transmits
Show plant pictures, what color of light is the plant absorbing, all except green. We see green because that is the color being reflected to our eyes, but really the color of a leaf is every other color but green.
If an object absorbs all wavelengths of visible light and no color reaches our eyes, the object appears ______________.
Black

3. I. Light
When sunlight (white light) passes through a prism, the different wavelengths of light separate into a spectrum of colors, which are?
ROYGBIV
Show plant pictures, what color of light is the plant absorbing, all except green. We see green because that is the color being reflected to our eyes, but really the color of a leaf is every other color but green.
Example: Rainbow

4. WHITE LIGHT

5. Electromagnetic spectrum
Consists of radiation over a broad band of wavelengths and frequencies.
What are some different types of radiation?
Ultraviolet, infrared, X-rays, gamma rays …
Can we see these different types of radiation?
No, Why?

6. Electromagnetic spectrum cont…
What is one type of radiation that we do see with our eyes, which is a small part of the electromagnetic spectrum?
Visible light
Light is just one form of electromagnetic radiation. But, the only one we can see
Visible light is just one form of electromagnetic radiation.

7. Electromagnetic Spectrum

9. The Microwave Oven
The microwave was invented after a researcher walked by a radar tube and a chocolate bar melted in his pocket.
Light is just one form of electromagnetic radiation. But, the only one we can see
Mmmmm… chocolate….

10. Visible Light
Exists at a wavelength of 1 x 10-7 m at a frequency of 1 x 1015 Hz on the electromagnetic spectrum.
Violet
Indigo
Blue
Green
Yellow
Orange
Red
400 nm
450 nm
All of these colors blend together at high frequencies to produce what color of light?
480 nm
500 nm
Do the demo with the fan and the light sticks.
560 nm
600 nm
White light nm

11. Visible Light cont…
Which color of light has the longest wavelength and the lowest frequency?
Red Light
Which color of light has the shortest wavelength and the highest frequency?
Violet light
The char. Is where you will always find that specific color of light.
The wavelength and frequency of each color of light is a __________ of that color.
quantitative characteristic

12. Wavelength and Frequency
What do we mean when we say the word “light” & how does this relate to wavelength and frequency?
waves
high
Light travels in ______ with either ____ or ___ frequencies at a speed of _____________ (in a vacuum).
low
3.00 x 108 m/s
c = speed of light = 3.00 x 108 m/s
What type of radiation refers only to that part of the electromagnetic spectrum that we can see with the human eye?
Visible Light

13.  Definitions: Origin is where each wave cycle begins.
Define amplitude.
Height of the wave from the origin to the crest (top of wave)
Define wavelength. ()
Symbol
Distance between two crests 
Define frequency. (ν)
# of wave cycles to pass a given point per unit of time.

14. In a wave:
C = V
Crest - top of the wave
Wavelength
Amplitude
Origin

15. In a wave cont …
As the wavelength of light increases (distance between the crests) what happens to the frequency?
decreases
Calculating the frequency of a wave:
ν = c λ
c = λν
s-1 = /sec
Cycles per second
The SI unit for frequency is:
Hertz (Hz) or s-1

16. Calculate the frequency of a wave whose wavelength is 6.0 x 10-5 cm.λ
6.0 x 10-5 cm 1 m
= 6.0 x 10-7 m
100 cm
s-1 = /sec
ν =
3.00 x 108 m/s
6.0 x 10-7 m
Convert cm to m by dividing by 100
= 5.0 x /s OR
= 5.0 x s OR
= 5.0 x Hz

17. Calculate the wavelength of the yellow light emitted by a sodium lamp
Calculate the wavelength of the yellow light emitted by a sodium lamp. The radiation frequency is 5.10 x 1014 s-1.
c = λν
c = λν ν ν
s-1 = /sec λ
= 3.00 x 108 m/s
= 5.88 x 10-7 m
Convert m to nm by multiplying by 109 (billion)
5.10 x 1014 /s
5.88 x 10-7 m
1 x 109 nm
= 588 nm 1 m

18. λ ν ν c = λν c = λν = 3.00 x 108 m/s = 4.76 x 10-7 m 6.30 x 1014 /s
Warm-up - Calculate the wavelength of a photon whose frequency is 6.30 x 1014 s-1.
c = λν
c = λν ν ν
s-1 = /sec λ
= 3.00 x 108 m/s
= 4.76 x 10-7 m
Convert m to nm by multipling by 109 (billion)
6.30 x 1014 /s
4.76 x 10-7 m
1 x 109 nm
= 476 nm 1 m

19. Warm-up - What color of light is produced?
= 476 nm
Blue-Indigo Light
Convert the wavelength to cm.
476 nm m 1
100 cm
Convert m to nm by multiplying by 109 (billion)
1 x 109 nm 1 m
= 4.76 x 10-5 cm

20. Atomic Emission Spectrum

21. III. Atomic Emission Spectrum
How do elements emit light in the gas state?
1 - Element is vaporized
2 - Pass an electric current through the gas
3 - The electrons in the atom absorb the energy which forces the e- to jump to high energy levels, known as the excited state.
4 - Then, the e- will lose the energy it has just gained and will fall back down to a lower energy level, known as the ground state.
The way it is working:
-         An element is vaporized
-         Pass energy, usually electricity, into it
-         The electrons absorb the energy and are forced to jump into a higher energy level
-         They don’t belong there and they don’t want to be there so they get rid of the energy as quick as they can, usually in the form of light.
-         When they lose the energy they are free to return to their proper energy level, their lowest energy level called the “Ground State”.
-         Pass the light emitted through a prism to get it’s atomic emission spectra for that particular element or compound.
The element or compound must be in a gaseous state.
What you get:
-         A series of bright lines
-         A fingerprint for that element or compound
5 - As the e- falls back to the ground state it will give off energy in the form of LIGHT.

22. III. Atomic Emission Spectrum cont..
Every element emits light!
Passing the emitted light from the element through a prism will give an
Atomic Emission Spectrum for that particular element.
These are distinct lines of color that correspond to exact wavelengths.
The way it is working:
-         An element is vaporized
-         Pass energy, usually electricity, into it
-         The electrons absorb the energy and are forced to jump into a higher energy level
-         They don’t belong there and they don’t want to be there so they get rid of the energy as quick as they can, usually in the form of light.
-         When they lose the energy they are free to return to their proper energy level, their lowest energy level called the “Ground State”.
-         Pass the light emitted through a prism to get it’s atomic emission spectra for that particular element or compound.
The element or compound must be in a gaseous state.
What you get:
-         A series of bright lines
-         A fingerprint for that element or compound
Each line corresponds to a specific amount of ________ being emitted.
energy

23. Atomic Emission Spectrum (slide)
Bands of Color

25. Light produced from an element can also be separated into distinct wavelengths
                       
Show this website to show students the different spectral lines for each element

26. III. Atomic Emission Spectrum cont..
How is the atomic emission spectrum useful?
Each element gives off a unique set of colors. The colored lines (or Spectral Lines) are a kind of "signature or fingerprint" for the element.
If you know the colors and the wavelengths you identify an unknown element

27. Atomic Emission Spectrum vs. White Light
(produced from either sun light or incandescent light bulbs)
gives a continuous spectrum of colors: the colors are blended together.
The way it is working:
-         An element is vaporized
-         Pass energy, usually electricity, into it
-         The electrons absorb the energy and are forced to jump into a higher energy level
-         They don’t belong there and they don’t want to be there so they get rid of the energy as quick as they can, usually in the form of light.
-         When they lose the energy they are free to return to their proper energy level, their lowest energy level called the “Ground State”.
-         Pass the light emitted through a prism to get it’s atomic emission spectra for that particular element or compound.
The element or compound must be in a gaseous state.
What you get:
-         A series of bright lines
-         A fingerprint for that element or compound

28. Whereas, an Atomic Emission Spectrum (produced from elements)
gives distinct bands of color (not all colors of the spectrum are present.
The colors of the lines are dependent upon the specific element.
These lines are called spectral lines.
Each line corresponds to one exact frequency of light emitted by the atom.
Atomic emission spectrum is for hydrogen

29. The instrument used to see spectral lines is called a spectrometer.
If you put light from a common streetlamp through a prism, or look at the light through a diffraction grating, you will see distinct lines. Two common kinds of street lights use sodium vapor and mercury vapor bulbs. Each of these lights has a different spectral "signature", and you can tell what kind of lamp it is by its spectral lines.

30. Examples: Na vapor emits a: Argon emits a: Krypton emits a:
Xenon emits a:
Neon emits a:
Orange-Yellow light
Lavender light
White light
Blue light
If you put light from a common streetlamp through a prism, or look at the light through a diffraction grating, you will see distinct lines. Two common kinds of street lights use sodium vapor and mercury vapor bulbs. Each of these lights has a different spectral "signature", and you can tell what kind of lamp it is by its spectral lines.
Red-orange light

31. Explanation of Atomic Spectrum
A single electron in the lowest energy level __________, can be excited to a higher energy level called the ___________.
ground state
excited state
Show plant pictures, what color of light is the plant absorbing, all except green. We see green because that is the color being reflected to our eyes, but really the color of a leaf is every other color but green.
The quantum of energy absorbed is equal to h x v

32. Planck showed mathematically that the amount of energy emitted or absorbed is proportional to the frequency of the radiation.
E = h v
h = Planck’s constant, x J•s
v = frequency, s-1 or /s
E = energy, J (joules)

33. The quantum of energy released is also equal to h x v
Then, the single electron drops back down from the ____________ to the ______ _____ and the electron releases energy in the form of electromagnetic radiation or _____.
excited state
ground
state
light
The same amount of energy gained is emitted (________) as a photon (______________).
released
quantum of light
Show plant pictures, what color of light is the plant absorbing, all except green. We see green because that is the color being reflected to our eyes, but really the color of a leaf is every other color but green.
The quantum of energy released is also equal to h x v
E = h v

35. Lyman Series Balmer Series Paschen Series
Three groups of lines are possible:
Lyman Series
Balmer Series
Paschen Series
e- drops from a high energy level to n=1, ultraviolet light is emitted
e- drops from a high energy level to n=2, visible light is emitted (ROYGBIV)
e- drops from a high energy level to n=3, infrared light is emitted

36. Bohr’s Model of the Atom
A photon is emitted or absorbed when electrons change energy levels
Bohr’s Model of the Atom