1. LIGHT
and
QUANTIZED ENERGY

2. To understand electric structure, therefore,
Much of our understanding of the electronic structure
of atoms has come from studying
how substances absorb or emit light.
To understand electric structure, therefore,
we must first understand light.

3. Visible light is only one type of
electromagnetic radiation.

4. There are many different types
of electromagnetic radiation.

5. Radio waves

8. Gamma rays are emitted from the
nucleus of some radioactive atoms.

9. The electromagnetic radiation is a form of energy
that has wavelike properties.

10. The electromagnetic spectrum contains
all the different types of electromagnetic radiation.

11. The different types of electromagnetic radiation
have different wavelengths and frequencies.

12. Wavelength The distance between two adjacent crests (or troughs)
is called the wavelength.
crest
trough
The unit for wavelength is meters, m.

14. The electromagnetic spectrum is arranged
in order of increasing wavelength.

15. The wavelengths of radio waves can be
longer than a skyscraper.

16. The wavelengths of gamma rays are as short
as the diameters of atomic nuclei.

17. Frequency The number of wavelengths that pass a given point
each second is the frequency of the wave.
(1 wave/s)
(1.5 wave/s)
(3 wave/s)

18. What is the frequency of each wave?
time(sec)
Frequency = ? 1 2
Frequency =
1/s ?
time(sec) 1 2

19. Frequency is expressed in waves per second, denoted /s or s-1.
Frequency is also expressed in hertz, Hz.
619 Hertz =
619 waves/sec
= 619/s
= 619 s-1
(1 wave/s)
(1.5 wave/s)
(3 wave/s)

20. Compare wave (A) to wave (C) in terms of wavelength and frequency.
Long wavelength
Low frequency
Short wavelength
High frequency

21. As the wavelength increases, the frequency ____________.
decreases
As the wavelength decreases, the frequency ___________.
increases

22. c = νλ All types of electromagnetic radiation
move through a vacuum at a speed of
3.00 x 108 m/s, the speed of light.
As a result, the wavelength and frequency
of electromagnetic radiation are related by:
Speed of light
Wavelength (lambda)
c = νλ
Frequency (nu)

23. c = νλ c c ν = λ = ν λ We can rearrange the equation to solve for
the frequency or the wavelength. c c
ν = λ = ν λ

24. c c ν = λ = ν λ The wavelength and the frequency
are inversely related.
As one increases the other decreases.
As one decreases the other increases.

25. c = νλ We can rearrange the equation to solve for
the frequency or the wavelength.

26. c λ = ν Calculate the wavelength of the yellow light
emitted by a sodium lamp if the frequency
of the radiation is 5.09 x 1014 Hz (5.09 x 1014 /s).
Given:
Equation:
ν = 5.09 x 1014 /s c λ =
c = 3.00 x 108 m/s ν
λ = ?

27. An gamma ray has a wavelength of 4.1 x 10-12 m. What is the frequency?
Given:
Equation:

28. A radio station broadcasts at a frequency of 590 kHz.
What is the wavelength of the radio waves?
Given:
Equation:

29. WHITEBOARD PRACTICE

30. 1. What is the frequency of orange light,
which has a wavelength of 6.09 x 10-7 m?
Given:
Equation:

31. 2. An electromagnetic wave has a frequency of 8. 70 X 1018 /s
2. An electromagnetic wave has a frequency of 8.70 X 1018 /s. What is its wavelength?
Given:
Equation:

32. 3. The yellow light given off by a sodium vapor lamp
used for public lighting has a wavelength of 589 nm.
What is the frequency of this radiation?
Given:
Equation:

33. The Particle Nature of Light
Thus far, we have learned that light and other radiation
behave like waves.
But light and other radiation also behave as if
composed of particles or rather packets of energy.
Energy is not absorbed
in a continues fashion.
in small specific amounts,
Energy is absorbed
in packets called quantum.
continues
stepwise

34. continues stepwise wavelike particle-like in small specific amounts,
Energy is absorbed
in packets called quantum.
Energy is not absorbed
in a continues fashion.
continues
stepwise
wavelike
particle-like

35. Radiant energy is quantized.
Matter can gain or lose energy only in small,
specific amounts called quanta (quantum).
That is, a quantum is the minimum amount of energy
that can be gained or lost by an atom.
Radiant energy is quantized.

36. A photon is quantum of radiant energy.
Electromagnetic radiation has both wavelike and particlelike characteristics.
Electromagnetic radiation can be thought of as
a stream of tiny particles, or bundles of energy,
called photons.
photon
A photon is quantum of radiant energy.

37. Energy of a photon = hν Ephoton = hν . where h = 6.626 x 10-34 J s
Planck’s constant
Ephoton = hν
Unit for energy
is the joule, J.
Frequency .
where h = x J s

38. c ν = = λ Ephoton = hν Ephoton = 2.88 x 10-19 J
What is the energy of one photon of red light?
The wavelength of red light is 690 nm. c
ν = =
4.35 x 1014 /s λ
Ephoton = hν
Ephoton = 2.88 x J

39. Energy of a photon = hν Ephoton = hν . where h = 6.626 x 10-34 J s
Planck’s constant
Ephoton = hν
Unit for energy
is the joule, J.
Frequency .
where h = x J s
The energy of a photon of light depends on the frequency,
the greater the frequency the greater the energy.

40. Ephoton = hν Which electromagnetic radiation carries the most energy?
Lower frequency
less energy
Higher frequency
More energy

41. As the frequency increases
The energy increases

42. Gamma rays have the highest frequency of all radiation,
as a result gamma rays have the greatest energy .

43. Tiny water droplets in the air disperse the white light
of the sun into a rainbow. What is the energy of a photon
from the violet portion of the rainbow if it has a
frequency of 7.23 x 1014 s-1?
Given:
Equation:
ν = 7.23 x 1014 /s
E = hν .
h = x J s
E = ?

44. Microwave ovens emit microwave energy with a wavelength of 12.9 cm.
What is the energy of exactly one photon
of this microwave radiation?
Given:
Equation:

45. What is the frequency of UV light that has
an energy of 2.39 x J? .
Given:
Equation:

46. WHITEBOARD PRACTICE

47. 4. What is the energy of radiation that has
a frequency of 4.2 X 1017 /s?
Given:
Equation:

48. 5. Calculate the energy of one photon of
orange light that has a wavelength of 605 nm.
Given:
Equation:

49. 6. Calculate the energy and frequency of
red light having a wavelength of 6.80 x 10-5 cm.
Given:
Equation:

50. 7. A ruby laser produces red light that has a
wavelength of 715 nm. Calculate its energy.
Given:
Equation:

51. A photon strikes an atom. If the photon contains enough energy,
the electron will jump to a higher energy orbital.
Excited electron

52. If the photon doesn’t contain enough energy,
the electron will remain in the ground state.

54. E = hν ∆E = Ehigher energy orbit – Elower energy orbit ∆E = ? ∆E = ?
What is the energy related to?
E = hν
If the ∆E is large,
the energy emitted will
have a _____ frequency
and a ________ wavelength.
∆E = ?
is large
high
short
∆E = ?
is small
If the ∆E is small,
the energy emitted will
have a _____ frequency
and a ________ wavelength.
low
long
∆E = Ehigher energy orbit – Elower energy orbit
Change in energy

55. As electrons return to the ground state, they emit a certain frequency of radiant energy.
Ephoton = hν

57. LAB: FLAME TEST

58. Each compound tested will produce a different color flame.
Flame colors are produced from the movement of the electrons
in the metal atoms present in these compounds.
For example, a sodium atom in its ground state has the electronic
configuration 1s22s22p6. When you heat the sodium atoms, the
electrons gain energy and jump into any of the empty orbitals
at higher levels - for example, into the 7s or 6p or 4d.

59. Because the electrons are now at a higher and more energetically unstable level, they tend to fall back down to the ground state.
As they return to the ground state, they emit photons of a specific energy.
This energy corresponds to a particular wavelength of light, and so produces particular colors of light. Each metal has a unique electron configuration.
The exact sizes of the possible jumps in energy terms vary from one metal to another.
That means that each different metal will produce a different flame color.

60. Lower energy
higher energy