THE NATURE OF LIGHT
1. Big Ideas:
Light has characteristics and properties that can be manipulated with mirrors and lenses
for a range of uses
2. Ministry Expectations:
Overall Expectations
E2. Investigate, through inquiry, the properties of light, and predict its behaviour
E3. Demonstrate an understanding of various characteristics and properties of light
Specific Expectations
E2.1 Use appropriate terminology related to light and optics [C]
E3.1 Describe and explain various types of light emissions
E3.2 Identify and label the visible and invisible regions of the electromagnetic spectrum
A1.11 Communicate using appropriate language
A1.12 Use appropriate numeric, and symbolic modes of representation, and appropriate
units of measurement
3. Student Learning Goals:
By the end of this lesson you will be able to identify and label the regions of visible and
invisible light on the electromagnetic spectrum.
By the end of this lesson you will understand how energy input/output and electron
movement within atoms produces light.
By the end of this lesson you will be able to describe the many different sources of light
and how they are produced.
4. Prior Knowledge:
SNC1D
C3.1 Explain how different atomic models evolved as a result of experimental evidence
C3.2 Describe the characteristics of neutrons, protons, and electrons, including charge,
location and relative mass
5. Rationale for Teaching and Learning Strategies:
(1) Minds on
Inquiry process (Predict/Explain/Observe/Explain): Activity based on internet
(YouTube) video by Bill Nye the Science Guy about the nature of light and colours. This
particular lesson would likely be the first in the unit on light and optics, therefore this
video provides a good introduction to the concepts that will be discussed in the unit,
while linking these concepts to prior knowledge that the students may have (outside of
formal classroom instruction) in the areas of light and colours. Students will be engaged
by observing the video and entering responses into a PEOE form, followed by teacherled questioning after each "explain" segment. This strategy allows for both 'assessment
for learning' and 'assessment as learning'.
(2) Action
Lecture: To teach the core material regarding electromagnetic spectrum, excitation and
emission of light, and the sources of light, a lecture-style strategy will be used. Although
in general teachers aim to minimize lecturing, this teaching strategy is only used in 15
minutes chunks, therefore it should not be too tedious for the students. Additionally, as
this component of the lesson teaches new material to the students, lecturing is an
effective method to pass along information that students can copy into their notebooks
and refer back to as they proceed onto later stages of the lesson. Other more studentactive strategies for this part of the lesson could be confusing, could be longer in
duration, and would likely not provide the students a resource (classroom notes)
Questioning: To review prior knowledge, a questioning approach will be used. Although
questioning will also be used throughout the entire lesson to assess student
comprehension, the review section will be entirely questioning to assess ‘for’ prior
knowledge of students. The required knowledge during this section comes from grade 9
science, and therefore may not be fresh in the students minds, so review is necessary to
move onward in the lesson. Questioning is a quick, information-rich, and relatively
stress-free method to teach/ review concepts. It also helps to determine a starting point
for the lesson. Questions may include those requiring individuals to answer, think-pairshare methods, or group discussions.
Simulation/ role playing game: To help cement the fundamental concept of electron
excitation and photon emission in the minds of the students, this fun activity uses the
students themselves for a demonstration of the sub-atomic events. This will appeal to
the kinesthetic learners who may struggle during lecture-style sections, and will also
reinforce the concepts for the visual and auditory learners. Students will have the
opportunity to participate in the activity, as well as observe it, which will give them two
points of view for understanding.
(3) Consolidation
Game/ peer practice: This simple game provides an opportunity for ‘assessment for
learning’ at the close of the lesson. Also, as it is active, student-oriented, and involves
teamwork, students will likely find it an appealing way to end the lesson. Furthermore,
because new knowledge is being assessed, and some students require extensive review
following a class for full understanding, to alleviate pressure on individual students to
answer correctly they will be working as a whole class and in pairs to complete the
activity.
(4) Next steps
Independent homework: To reinforce the knowledge attained during class time, the
students will complete a short but relevant homework assignment. Students will create
a concept map to demonstrate their understanding of the concepts discussed in class,
and the inter-connections between these concepts.
6. Assessment Strategies and Rationale
Game (matching cards game and electron movement game): the two games will both
asses ‘for’ student learning. For both, students must complete some independent
thinking, but will also be able to work in groups, or as a class – therefore these games
asses individual student learning and whole class understanding, as well as overall
success of the teacher. If students are struggling with either game, perhaps re-teaching
will be required. Both games come immediately following lessons on the particular
material, therefore it will directly assess the learning of the students based on the class
work.
Questioning: This strategy of assessment will be used throughout the lesson, but
particularly during the review sections and the lecture-style sections. Questioning
assesses ‘for’ learning, and provides information on the ability of the students to
understand the knowledge that was presented. This strategy is useful because it
provides quick feedback, and because a teacher can easily assess the knowledge of
individual students, or of the whole class if discussions/ brainstorming/ think-pair-share/
thumbs up & thumbs down methods are used.
Homework (concept map): this strategy assesses ‘for’ learning, and incorporates all the
information given during the class period into one assignment. This measures not only
the individual understanding of each student, but also their ability to inter-connect the
concepts presented in class. This type of strategy can indicate clearly whether or not a
student understands the material. This would be given as a homework assignment at
the end of class – so that the students would complete it independently and also so that
the students have been given all the knowledge required for the assessment. 7.
7. Summary Chart for Lesson
Time
Teaching/
Learning
Strategies
What the teacher
will do
Minds On (Elicit and Engage)
0–
A: Inquiry
Start showing the
0:10
process
video; pause for
(PEOE)
students to fill in
“PE” portion of
PEOE; then finish
showing video;
allow students to
complete PEOE,
and then pose
questions
Action (Explore, Explain)
0:10 – B: Lecture
Lecture on EM
0:25
radiation, with
frequent
questioning
0:25 – C:
Draw Bohr0:35
Questioning/ Rutherford model
Lecturing
on the chalkboard.
Demonstrate how
light is made at the
atomic level, using
students prior
knowledge as a
base
0:35 – D: Simulation/ Explain the game
0:50
role playing
and then verify that
game
students proceed
correctly
What students
will do
Ready-to-use
support materials,
supplies and
equipment for the
lesson
Watch video
about the nature
of light and fill in
PEOE about
several questions
that arise
A1: YouTube video
on the nature of
light, projector/
computer (CRM)
(TN)
A2: PEOE worksheet
(CRM)
Copy chalkboard
notes and
respond to
questions
Copy chalkboard
notes and
respond to
questions
B1: Chalkboard
notes (SN)
B2: Questioning
sequence (TN)
C1: Chalkboard
notes (SN)
C2: Questioning
sequence (TN)
Following the
rules of the
game, use
themselves as
demonstrations
of electrons being
excited by
incoming energy
and releasing
photons as they
return to lower
energy states
D1: Small step, chair,
desk, see-saw, small
balls of different
colours, four books
(CRM)
D2: Envelopes with
energy levels (CRM)
D3: Explanation of
game (TN)
0:50 – E: Lecture
1:05
Lecture on the
sources of light,
with frequent
questioning
Consolidation (Elaborate, Evaluate, Extend)
1:05 – F: Game/ Peer Explain the game
1:15
practice
and then verify that
students proceed
correctly
Next Steps
At
G: Homework
Home
Collect concept
maps during the
next class and
assess for learning
– giving feedback
Copy chalkboard
notes and
respond to
questions
E1: Chalkboard
notes (SN)
Using the
provided cards,
find a partner
whose card
matches their
own to form a
reasonable
pairing and then
briefly present to
the class why
their cards match
F1: Cue cards with
terms or definitions
describing the
nature of light/
sources of light/
excitation of
electrons etc. (CRM)
F2: Explanation of
the game (TN)
Create a concept
map of the
concepts
discussed in class
G1: Explanation of
homework (TN)
8. Student "Chalkboard" Notes
B1: Chalkboard notes on electromagnetic spectrum
Wavelength: The special period of the wave, or the distance over which the wave’s
shape repeats (lambda symbol)
Nanometer: 10-9 meters
Humans can only detect light between 400-750 nm (ROYGBIV), but other animals (bees)
can see UV and some snakes can detect infrared.
C1: Chalkboard notes on excitation of atoms
1. An atom absorbs energy an electron moves to a higher orbital giving it potential
energy. Atom is in “excited state”
2. Electron eventual returns to “ground state” giving off energy in form of a photon
3. A photon is a “discreet packet of energy”
4. Photon travels as a wave, if it’s between 400-750 nm, humans see it as light.
E1: Chalkboard notes on sources of light
Luminous
A material that produces its own light.
Examples: sun, light bulb, flashlight, match
Non-luminous
A material that does not produce its own light – it can be seen only by using reflected
light.
Examples: pencil, tree, desk
“We don’t see things; we see light bouncing off of things.” - Bill Nye the Science Guy
Incandescence
Incandescent light is produced when hot matter releases parts of its thermal vibrational
energy as photons. As any object gets hotter and hotter will eventually produce light (by
470°C virtually all substances will glow).
Examples: stove element, Bunsen burner flame, volcano lava
Incandescent Light Bulbs have a thin wire filament of tungsten inside a bulb that is filled
with non-reactive gases. As electricity passes through the filament, it becomes so hot it
gives off light (visible and IR) and it glows. These light bulbs are inefficient: only 5-10% of
electricity goes to making visible light.
Fluorescence
The immediate emission of visible light as a result of the absorption of UV light.
Examples: highlighter pens, fluorescent lights
Fluorescent Lights are made from a tube filled with very low pressure mercury vapour
and coated with fluorescent material on the inner surface. The electric current causes
the mercury atoms to emit UV light, which strikes the fluorescent inner surface of the
tube, resulting in the producing of visible light.
Phosphorescence
The processes of producing light by the absorption of UV light resulting in the emission
of visible light (lower energy) over an extended period of time. The time delay is due to
quantum mechanical energy state transitions, which can cause the energy to become
trapped and the electron cannot return to the ground state immediately by using
normal conditions.
Examples: glow-in-the-dark stickers, watches
Electric discharge
The process of producing light by passing an electric current through a gas. The
electricity causes the gas to glow.
Examples: neon light, lightning
Chemiluminescence
The direct production of light as a result of a chemical reaction with little or no heat
produced.
Examples: glow stick
Bioluminescence
The production of light in living organisms as a result of a chemical reaction with little or
no heat produced.
Examples: firefly, glow-worm
Triboluminescence
The production of light as a result of friction as a result from scratching, crushing, or
rubbing certain crystals.
Examples: rubbing together two quartz crystals
Light-emitting diode (LED)
Light produced as a result of an electric current flowing in semiconductors. Allows light
to flow in only one direction (by use of semiconductors).
Examples: Christmas lights, small red light to show that radio is on
9. Classroom Ready Materials
A2: PEOE worksheet
PEOE Activity - Bill Nye and the
Nature of Light
Predict
Explain
Observe
Explain
D2: Student Activity: human simulation of electron excitation and photon emission –
envelope contents
Listed below are the contents of the envelopes and in [square brackets] are the
expected student actions – note that these student actions will not be listed on the
cards, but rather the students (in consultation with classmates if required) must
determine their actions.
1. You do not receive any additional energy [remain in ground state (first energy
level) – stay on ground]
2. You receive a low-energy photon in the red visible colour range [low energy
photon absorption – move up to the second energy level/ small step]
3. You receive a medium-energy photon in the yellow visible colour range [medium
energy photon absorption – move up to the third energy level/ chair]
4. You receive a high-energy photon in the violet visible colour range [high energy
photon absorption – move up to the fourth energy level/ desk]
For the second round, hydrogen atoms in particular will be examined. Listed below are
the contents of the envelopes for this second part of the activity.
1. You do not receive any additional energy [remain in ground state – stay on
ground]
2. You receive a medium-energy photon [medium energy photon absorption –
move up to the third energy level/ chair]
3. You receive a high-energy photon [high energy photon absorption – move up to
the fourth energy level/ desk]
4. You receive a very high-energy photon [very high energy photon absorption –
move up to the fifth energy level/ book placed on top of desk]
5. You receive a very, very high-energy photon [very, very high energy photon
absorption – move up to the sixth energy level/ 2 books placed on top of desk]
F1: Student Activity: matching game – card contents
Round 1
1. non-luminous – pencil
2. incandescence – stove element
3. fluorescence – highlighter pen
4. phosphorescence – glow-in-the-dark watch
5. electric discharge – neon light
6. chemiluminescence – glow stick
7. bioluminescence – fire fly
8. LED – Christmas lights
9. luminous – a material that produces its own light
10. incandescence – light that is produced when hot matter releases energy as
photons
11. electric discharge - the process of producing light by passing an electric current
through a gas
12. chemiluminescence - the direct production of light as a result of a chemical
reaction with little or no heat produced
13. bioluminescence - the production of light in living organisms as a result of a
chemical reaction with little or no heat produced
14. triboluminescence - the production of light as a result of friction as a result from
scratching, crushing, or rubbing certain crystals
15. LED - light produced as a result of an electric current flowing in semiconductors
Round 2
1. dispersion – the separation of white light into its constituent colours
2. visible light –
3. electromagnetic spectrum – radio waves, microwaves, infrared light, visible light,
ultraviolet light, X-rays, gamma rays
4. wavelenght of violet light – 400 nm
5. wavelength of red light – 700 nm
6. 1 nm = 1 x 10-9 m
eeP
N
e-
7. Bohr-Rutherford model –
ee-
e-
8. absorption of a photon – causes excitation of an electron into a higher energy
state
9. emission of a photon – causes relaxation of an electron down to a lower energy
state
10. subatomic particles in the nucleus – protons and neutrons
11. subatomic particles outside of the nucleus – electrons
12. incandescent light bulb –
13. fluorescent light bulb –
14. electromagnetic radiation with a very long wavelength – radio waves
15. electromagnetic radiation with a very short wavelength – gamma rays
10. Teacher Notes
A1: PEOE Activity – video notes
Set up YouTube video to show the following portions of the video
(A) 0:50 – 2:44 Dispersion of light
(B) 3:44 – 4:30 Colours of fruits and vegetables
(C) 5:15 – 7:19 Absorption and reflection of light
To begin, ask the students to fill in the PE portions of the PEOE in the top slot for the
following question:
(1) In the summer, why do you feel so much hotter when you wear black clothes
and so much cooler when you wear white clothes?
Ask the students to fill in the PE portions of the PEOE in the bottom slot for the
following question:
(2) What happens when you mix together all the different colours of paint (ex red,
orange, yellow, green, blue, purple)?
Show video clips (A), (B), and (C), which answer these questions.
Have the students fill in the OE portions of the PEOE while watching the video.
As a class discuss the answers to (1) and (2) in terms of the nature of light.
B2: Questioning sequence for EM spectrum
Q1: What do you notice about the nature of the wave’s shape as it moves left to right?
Q2: Between what two types of light do you think visible light will fall?
Q3: What’s a nanometer?
C2: Questioning sequence for photon emission
Q1: Describe the Bohr-Rutherford model of an atom.
Q2: Based on what you know from the EM spectrum, how is the wavelength of a photon
related to its energy
Q3: Which would emit a photon of greater energy, an electron returning to ground state
from n=6 or n=8?
D3: Student Activity: human simulation of electron excitation and photon emission
The front of the classroom will be set up with a small step, a chair, a desk, and a see-saw
as below:
Several student volunteers will come to the front and they will be given an envelope
with a cue card inside. These cue cards will contain information about how, and how
much energy they have been given. The students (acting as electrons) will then stay in
the ground state – first energy level (stand on the ground), move up one energy level –
second energy level (to the step), two energy levels – third energy level (to the chair), or
three energy levels – fourth energy level (to the desk). After a period of time
(dependent upon the stability of the energy level to which they have been promoted)
the student will jump back down to the ground state. When they do so, they will land on
a see-saw with a coloured ball placed on the opposite side. When they land the ball (a
photon) will be emitted (sent up into the air). Depending on the energy level from which
they are falling, the photon will have a certain energy itself (indicated by how high it is
sent into the air).
After several trial runs, the activity will be repeated specifically using the hydrogen
atom. This time, different coloured balls will be used, and as the students jump back
down to the ground state, the colours will indicate the energy of the photon and the
colour of light that is ultimately produced.
Here it should be pointed out that the electrons do not always fall directly down to the
ground state as they emit a photon. In fact, in every case where visible light is emitted
from a hydrogen atom, the electron is falling from a higher energy level down to the
ENERGY LEVEL ABOVE the ground state (i.e. level 2). Although we will not attempt to
place a see-saw on top of the small step, because this would be too dangerous, we can
pretend that the see-saw has now been elevated to the second energy level. Also –
higher energy levels will be required: the fifth energy level will be a book on top of the
desk, and the sixth is 2 stacked books on top of the desk
The Balmer series (of photon emission from hydrogen) is partially in the visible region.
The four examples in the envelopes are the electron movements responsible for the
four emission spectrum bands in the visible region. Have the students guess which
student electron is responsible for each one, and allow them to jump down onto the
see-saw with the appropriately coloured ball to show photon emission of that colour.
The EM spectrum can be on the overhead for the students to compare the wavelengths
and energy levels of each of these. [3  2 red (656.3 nm); 4  2 cyan (486.1 nm); 5 2
blue (434.0 nm); 6 2 violet (410.2 nm)]
Note: this could be a very dangerous activity, so be sure that the students are jumping
carefully and that the see-saw is stable and the students will not fall backwards if they
miss. Also, practice a few trial runs before class to verify that the balls will not be sent
flying and the remaining observing classmates.
F2: Student Activity: consolidation of lesson concepts – matching game
Students will each be given a set of cue cards with either a term, a definition, an
example, or a picture. Each of these cards has a matching card (example: term –
definition; term – example; definition – picture) given to another student in the class. All
cards relate to the concepts covered in class, including the electromagnetic spectrum,
electron excitation, photon emission, and sources of light.
Students must correctly match their card to the card of a classmate, and then once all
students have been matched, each pair presents their cards and the class decides if they
agree or disagree with the pairing by a show of hands. There will be several rounds of
the game, so the cue cards will be colour coded to make sure that the wrong cards will
not be matched during the wrong round.
Note: the matching cards used will have to be selected carefully based on the number of
students in the class, to make sure that each student has a partner. This class set was
based on a class of 30 students. Alternatively, all cards could be used, and the extra
cards can be placed at the front of the room – if students cannot find a partner, they can
search the cards at the front for a match.
G1: Homework: concept map
Students will complete a concept map, to be collected in class the following day. The
concept map will be used to assess for student learning, and will be included in the
learning skills and work habits portion of the student report card, but will not be
evaluated with a letter grade. Students can create their concept map by hand, or on the
computer; it can be coloured or black and white; it can be text only, pictures only or a
combination of pictures and text. It should include all concepts discussed in class,
including: the electromagnetic spectrum, electron excitation, photon emission, and
sources of light.
11. References
Bill Nye the Science Guy (January 14, 2009). Bill Nye the Science Guy light & colour 1of3.
Retrieved from http://www.youtube.com/watch?v=KvOs_RBjLOk
Dickinson, T., Edwards, L., Flood, N., Grace, E., Jackson, C., Mazza, M., Ross, J., (2009).
ON Science 10. (1st ed.). Whitby. (ON). McGraw-Hill Ryerson Ltd.
DiGiuseppe, M., et al. (2010). Science perspectives 10. (1st ed.). Toronto, (ON): Nelson
Education Ltd.