Light imitates art
View Sequence overviewStudents will:
- identify materials as transparent, translucent or opaque.
- define ‘transparent’, ‘translucent’ and ‘opaque’.
- identify and define shadows, including the umbra and penumbra.
- explain how shadows can change shape and size.
Students will represent their understanding as they:
- categorise materials as transparent, translucent or opaque.
- draw a ray diagram to show the formation of a shadow.
- contribute to discussions to define and explain how shadows are formed and manipulated.
In this lesson, assessment is formative.
Feedback might focus on:
- students’ descriptions and definition of a shadow.
- students’ ray diagrams—are they accurately representing the direction the light is travelling? Do they show the light hitting the object and how a shadow is formed? Have they included arrows to indicate the direction of travel?
Whole class
Class science journal (digital or hard-copy)
Materials to create a word wall
2 torches
Demonstration copy of Passing through Resource sheet
Demonstration copy of I can see the light Resource sheet
Demonstration copy of Shadow masters Resource sheet
Objects to create a shadow for demonstration purposes
Demonstration copy of Umbra and Penumbra Resource sheet
A dark coloured object, such as a piece of black paper/cardboard, a book with a dark coloured cover, etc.
Each group
A selection of materials for students to test, which are:
- transparent, e.g. cling wrap, certain plastic containers, food wrappings, glass, cellophane
- translucent, e.g. baking paper, tissues/tissue paper, frosted glass/plastic, sheer fabric
- and opaque, e.g. most things that can be easily sourced in the classroom, including paper, books, pencil cases, digital devices, erasers, desks
Torch
3 opaque objects, one with straight edges, one with curved edges and one of their choosing (see lesson steps for suggestions)
Each student
Individual science journal (digital or hard-copy)
Passing through Resource sheet (or create their own)
Shadow masters Resource sheet
Lesson
Re-orient
Review the previous lesson. Discuss what happened when the light hit the bend in the tube of paper, what happened when it hit the reflective surface, and how these actions were different.
The Inquire phase allows students to cycle progressively and with increasing complexity through the key science ideas related to the core concepts. Each Inquire cycle is divided into three teaching and learning routines that allow students to systematically build their knowledge and skills in science and incorporate this into their current understanding of the world.
When designing a teaching sequence, it is important to consider the knowledge and skills that students will need in the final Act phase. Consider what the students already know and identify the steps that need to be taken to reach the level required. How could you facilitate students’ understanding at each step? What investigations could be designed to build the skills at each step?
Read more about using the LIA FrameworkIdentifying and constructing questions is the creative driver of the inquiry process. It allows students to explore what they know and how they know it. During the Inquire phase of the LIA Framework, the Question routine allows for past activities to be reviewed and to set the scene for the investigation that students will undertake. The use of effective questioning techniques can influence students’ view and interpretation of upcoming content, open them to exploration and link to their current interests and science capital.
When designing a teaching sequence, it is important to spend some time considering the mindset of students at the start of each Inquire phase. What do you want students to be thinking about, what do they already know and what is the best way for them to approach the task? What might tap into their curiosity?
Read more about using the LIA FrameworkHow dull!
Note that not all surfaces are reflective, and ask students how they might describe the surfaces of other objects (dull, rough, dark, etc.).
Pose the question: What happens when light hits different surfaces? What will it do?
Examine some different materials that are available for students to test.
Students predict if they think the materials will let ‘lots of light’ or ‘some light’ or ‘no light’ through. Ask students to give reasons for their predictions.
Note: It is important to delineate between ‘material’ as what something is made of’, and an object. For example, a window is an object, but the material they are made from is typically glass, with a metal, plastic or wooden frame. Where possible students should be encouraged to list the specific material rather than the object. This is because transparency, translucency and opaqueness are properties of materials and not objects. Students will be familiar with materials and their properties from past learning in chemical sciences in Foundation and Years 2 and 4.
The Inquire phase allows students to cycle progressively and with increasing complexity through the key science ideas related to the core concepts. Each Inquire cycle is divided into three teaching and learning routines that allow students to systematically build their knowledge and skills in science and incorporate this into their current understanding of the world.
When designing a teaching sequence, it is important to consider the knowledge and skills that students will need in the final Act phase. Consider what the students already know and identify the steps that need to be taken to reach the level required. How could you facilitate students’ understanding at each step? What investigations could be designed to build the skills at each step?
Read more about using the LIA FrameworkThe Investigate routine provides students with an opportunity to explore the key ideas of science, to plan and conduct an investigation, and to gather and record data. The investigations are designed to systematically develop content knowledge and skills through increasingly complex processes of structured inquiry, guided inquiry and open inquiry approaches. Students are encouraged to process data to identify trends and patterns and link them to the real-world context of the teaching sequence.
When designing a teaching sequence, consider the diagnostic assessment (Launch phase) that identified the alternative conceptions that students held. Are there activities that challenge these ideas and provide openings for discussion? What content knowledge and skills do students need to be able to complete the final (Act phase) task? How could you systematically build these through the investigation routines? Are there opportunities to build students’ understanding and skills in the science inquiry processes through the successive investigations?
Read more about using the LIA FrameworkPassing through
In collaborative teams, students use the Passing through Resource sheet to record a list of materials they will test and make a prediction as to how much light they think each material will let through.
They shine a light on each material to test it and record their observation by categorising the materials as letting ‘lots of light’, ‘some light’ or ‘no light’ through.
The Inquire phase allows students to cycle progressively and with increasing complexity through the key science ideas related to the core concepts. Each Inquire cycle is divided into three teaching and learning routines that allow students to systematically build their knowledge and skills in science and incorporate this into their current understanding of the world.
When designing a teaching sequence, it is important to consider the knowledge and skills that students will need in the final Act phase. Consider what the students already know and identify the steps that need to be taken to reach the level required. How could you facilitate students’ understanding at each step? What investigations could be designed to build the skills at each step?
Read more about using the LIA FrameworkFollowing an investigation, the Integrate routine provides time and space for data to be evaluated and insights to be synthesized. It reveals new insights, consolidates and refines representations, generalises context and broadens students’ perspectives. It allows student thinking to become visible and opens formative feedback opportunities. It may also lead to further questions being asked, allowing the Inquire phase to start again.
When designing a teaching sequence, consider the diagnostic assessment that was undertaken during the Launch phase. Consider if alternative conceptions could be used as a jumping off point to discussions. How could students represent their learning in a way that would support formative feedback opportunities? Could small summative assessment occur at different stages in the teaching sequence?
Read more about using the LIA FrameworkTransparent, translucent or opaque?
Share results as a class, grouping together materials according to how much light they let through.
Allow students to name each category.
If students do not offer them, introduce the terms (without definitions) ‘transparent’, ‘translucent’ and ‘opaque’. Ask students if they have heard these terms before, what they know about them, and which they would attach to each category.
Ask students if they can describe how clearly you can see objects through transparent, translucent and opaque materials.
Introduce the definitions for each of the above terms, and compare them to the students’ ideas:
- Transparent: Light is transferred through the material in a straight line. You can see what is on the other side of the material clearly.
- Translucent: Light is scattered as it travels through the material. Some light may be absorbed. You can see some things that are on the other side of the material, but they are not clear. Materials can have different 'levels' of translucence.
- Opaque: Light cannot travel though the material. The path of the light will be blocked and a shadow will be formed. You cannot see through the material.
If groups have categorised the same materials differently, discuss how/why they made different decisions. Discuss if, when and why categorising the items differently might cause problems, and how scientists might go about ensuring that this doesn't happen: Scientists use/design and build specialised equipment and agree on universal standards to make sure that results are fair and not subject to personal opinions or ideas. For example, a light meter measures the amount of light in ‘lux’ units, and is an impartial, fair and accurate way to determine levels of light.
Record the names of the materials on a demonstration copy of the I can see the light Resource sheet. Invite students to name other materials/objects that could be added to each category. If required, discuss the material/object and reach a class consensus over which category it belongs in before adding it to the resource sheet.
The Inquire phase allows students to cycle progressively and with increasing complexity through the key science ideas related to the core concepts. Each Inquire cycle is divided into three teaching and learning routines that allow students to systematically build their knowledge and skills in science and incorporate this into their current understanding of the world.
When designing a teaching sequence, it is important to consider the knowledge and skills that students will need in the final Act phase. Consider what the students already know and identify the steps that need to be taken to reach the level required. How could you facilitate students’ understanding at each step? What investigations could be designed to build the skills at each step?
Read more about using the LIA FrameworkIdentifying and constructing questions is the creative driver of the inquiry process. It allows students to explore what they know and how they know it. During the Inquire phase of the LIA Framework, the Question routine allows for past activities to be reviewed and to set the scene for the investigation that students will undertake. The use of effective questioning techniques can influence students’ view and interpretation of upcoming content, open them to exploration and link to their current interests and science capital.
When designing a teaching sequence, it is important to spend some time considering the mindset of students at the start of each Inquire phase. What do you want students to be thinking about, what do they already know and what is the best way for them to approach the task? What might tap into their curiosity?
Read more about using the LIA FrameworkAbsorbing ideas
Focus on the list of opaque objects, and pose the question: What happens when light hits an opaque object?
Students share their ideas and predictions, based on the experience they have just had shining light on materials that have been classified as opaque.
The Inquire phase allows students to cycle progressively and with increasing complexity through the key science ideas related to the core concepts. Each Inquire cycle is divided into three teaching and learning routines that allow students to systematically build their knowledge and skills in science and incorporate this into their current understanding of the world.
When designing a teaching sequence, it is important to consider the knowledge and skills that students will need in the final Act phase. Consider what the students already know and identify the steps that need to be taken to reach the level required. How could you facilitate students’ understanding at each step? What investigations could be designed to build the skills at each step?
Read more about using the LIA FrameworkThe Investigate routine provides students with an opportunity to explore the key ideas of science, to plan and conduct an investigation, and to gather and record data. The investigations are designed to systematically develop content knowledge and skills through increasingly complex processes of structured inquiry, guided inquiry and open inquiry approaches. Students are encouraged to process data to identify trends and patterns and link them to the real-world context of the teaching sequence.
When designing a teaching sequence, consider the diagnostic assessment (Launch phase) that identified the alternative conceptions that students held. Are there activities that challenge these ideas and provide openings for discussion? What content knowledge and skills do students need to be able to complete the final (Act phase) task? How could you systematically build these through the investigation routines? Are there opportunities to build students’ understanding and skills in the science inquiry processes through the successive investigations?
Read more about using the LIA FrameworkForming shadows
Explore students’ ideas and predictions and demonstrate what happens by shining a light on an opaque object so that a shadow is formed.
Once students have identified the shadow, explain that they are going to further explore shadows in the following investigation.
Using a demonstration copy of the Shadow masters Resource sheet, discuss:
- What does a shadow look like (shape, colour)?
- Will the shadow always be the same on any surface?
- Does the shape of the object make a difference?
- Does the edge of the object (straight, curved, soft, translucent) make a difference?
Discuss the objects the students might select to make shadows with: one with straight edges, one with curved edges, and one of their choosing. This third object might have soft edges, include opaque and transparent materials, have holes in it, or have movable parts.
Students select one object to draw ray diagrams (with arrows) to show the shadows that are formed.
Allow students time to complete their observations in collaborative teams, recording their observations and drawing their ray diagrams individually.
Optional: Students see if they can manipulate the shapes from the shadows into something else, for example manipulating a circle into a love heart, or outlining a shadow and adding lines and features to make it appear like an animal. Explore the work of Vincent Bal at the Vincent Bal Shadowology YouTube channel for inspiration.
Alternative conceptions—shadows
What alternative conceptions might students hold about shadows?
Shadows occur when the path of light is blocked by an object. A shadow is formed on the opposite side of the object from the light source. The object, shadow and light source are in line with each other because light travels in approximately a straight line. The closer the object is to the light source the larger the shadow. This is because it blocks out more of the light. If the object is further away from the light source it will block less of the light. This will produce a smaller shadow.
Students might have non-scientific ideas about shadows. They might think that shadows exist independently of an object rather than being directly connected to an object. Some students consider them to be copies of the object rather than silhouettes. Others confuse shadows with reflections, which occur when light bounces off a surface into our eyes, allowing us to see an image.
Shadows are caused by an object blocking the transfer of light. They can only be seen if light is prevented from reaching an object or surface. Their size and shape depend on the position of the light source, the properties of the object itself and the distance to the surface from which the light is blocked.
This lesson addresses these alternative conceptions by supporting students to directly see that shadows are created when light from a source is blocked by an object, including that the shadow's size and shape is related to the object itself. Students can explore how they can manipulate the size and shape of a shadow by changing the position of the light source. They continue this exploration in Lesson 5.
Shadows occur when the path of light is blocked by an object. A shadow is formed on the opposite side of the object from the light source. The object, shadow and light source are in line with each other because light travels in approximately a straight line. The closer the object is to the light source the larger the shadow. This is because it blocks out more of the light. If the object is further away from the light source it will block less of the light. This will produce a smaller shadow.
Students might have non-scientific ideas about shadows. They might think that shadows exist independently of an object rather than being directly connected to an object. Some students consider them to be copies of the object rather than silhouettes. Others confuse shadows with reflections, which occur when light bounces off a surface into our eyes, allowing us to see an image.
Shadows are caused by an object blocking the transfer of light. They can only be seen if light is prevented from reaching an object or surface. Their size and shape depend on the position of the light source, the properties of the object itself and the distance to the surface from which the light is blocked.
This lesson addresses these alternative conceptions by supporting students to directly see that shadows are created when light from a source is blocked by an object, including that the shadow's size and shape is related to the object itself. Students can explore how they can manipulate the size and shape of a shadow by changing the position of the light source. They continue this exploration in Lesson 5.
The Inquire phase allows students to cycle progressively and with increasing complexity through the key science ideas related to the core concepts. Each Inquire cycle is divided into three teaching and learning routines that allow students to systematically build their knowledge and skills in science and incorporate this into their current understanding of the world.
When designing a teaching sequence, it is important to consider the knowledge and skills that students will need in the final Act phase. Consider what the students already know and identify the steps that need to be taken to reach the level required. How could you facilitate students’ understanding at each step? What investigations could be designed to build the skills at each step?
Read more about using the LIA FrameworkFollowing an investigation, the Integrate routine provides time and space for data to be evaluated and insights to be synthesized. It reveals new insights, consolidates and refines representations, generalises context and broadens students’ perspectives. It allows student thinking to become visible and opens formative feedback opportunities. It may also lead to further questions being asked, allowing the Inquire phase to start again.
When designing a teaching sequence, consider the diagnostic assessment that was undertaken during the Launch phase. Consider if alternative conceptions could be used as a jumping off point to discussions. How could students represent their learning in a way that would support formative feedback opportunities? Could small summative assessment occur at different stages in the teaching sequence?
Read more about using the LIA FrameworkLight and heat energy
Before beginning the Integrate discussion, set up a torch so that it is shining directly onto an opaque object—something dark, like a black piece of paper, will work most effectively. Focus as much of the beam of light as possible directly onto the paper, so that no (or very little) shadow is formed. Leave the torch switched on for the duration of the discussion, so that the object warms up. Draw students’ attention to what you have set up (without explaining why), informing them you will come back to it as the last part of the discussion.
Share and discuss what happened during the Shadow masters investigation.
- What happened when you shone the light from the torch onto an opaque object?
- A shadow was formed.
- What is a shadow?
- A dark area behind an object.
- Why is it dark behind the object?
- Because the light is blocked by the object, so the light can’t get behind it. Light passing the edges of the object defines the dark part.
- Can you explain what is happening?
- Can you change the shape of a shadow? How?
- How did the shape of the object affect the shadow?
- What was the third object you chose? Why did you choose that? What kind of shadow did it make? What was interesting about its shadow?
- Can we see any detail in the shadow (the colour or any patterns)?
- Is a shadow completely black?
- No, not always. Sometimes a shadow has a dark section, and a lighter section.
- Why do you think that is?
- Do you think transparent or translucent objects/materials will cast shadows? Why do you think that?
Create a shadow using an object and asks students to describe what they observe or notice about the shadow formed. If necessary guide them to notice the ‘umbra’ (the inner darker part of a shadow) and ‘penumbra’ (the lighter part of a shadow)—using an object with lots of edges, protuberances or moving parts will create the best results. Also experiment with the angle of the light source before the demonstration to see which casts the most effective shadow for this purpose.
Discuss with students why they think that some parts of the shadow are lighter/darker.
Introduce the terms ‘umbra’ and ‘penumbra’, show students a diagram representing the phenomenon (as seen below), either using the demonstration copy of Umbra and Penumbra Resource sheet or drawing your own relevant to the object you are using to create the shadow.
Allow students time and opportunity to discuss what the diagram is representing.
As required, prompt students with questions and comments to reach the conclusion that, because the light from a broad/wide/large source is travelling in more than one direction/angle, the main shadow (umbra) is formed where all light is blocked, and a second shadow (penumbra) is formed around the edges where only some of the light is blocked.
Draw students’ attention back to the beam of light you focused on the opaque object at the start of the discussion and discuss what is happening.
- Where is the light shining?
- What is happening to the light as it hits the object/paper? Is a shadow being formed?
- No, because the beam of light is not wide enough to ‘get around’ the object/paper in order to make a shadow.
- So, what is happening to the light? Where is it going?
- Students might express that the light is disappearing, or ‘going into’ the paper. This is acceptable at this point.
Turn off the torch and ask some students to feel the section of the paper that the beam of light was directed at. You will need to do this quickly, as the heat generated will rapidly begin to dissipate. Discuss.
- What does the paper feel like where the beam of light had been shining?
- It was warm to the touch.
- What do you think was happening?
- The light made the paper warm. The light turned into heat.
- Scientists use the word ‘transfer’/‘transferred’ to describe what is happening when one form of energy turns into another. In this case, light turning into heat. Could you use the words transform/transformed to describe what happened to the light as it hit the paper?
Through prompting and discussion, support students to come up with an explanation about what is happening in terms of the transformation of energy when light is absorbed by an opaque material.
- Where does the light go when it hits an opaque material?
- The light can't get through the material, so it goes into the material, gets "soaked up", "sucked in", or absorbed.
- Note that students might use everyday language to describe what happens. This language should be accepted as it will help students to understand what is happening, and then connected with the correct scientific terminology: being absorbed.
- As the light is absorbed it turns into heat energy.
- The light can't get through the material, so it goes into the material, gets "soaked up", "sucked in", or absorbed.
- If students have already learned about particles of materials in Year 5 Chemical sciences: What do you think is happening to the particles that make up the opaque material? How are they behaving?
- The particles are vibrating faster and more strongly—that's why the material feels hotter.
- Is light "hot"? If you held your hand in front of a torch would it feel warm straight away, or take some time to feel warm?
- When you hold your hand in front of the beam of a torch it doesn't feel hot, but if you left your hand there for a while it would eventually become warm. More light energy is absorbed and transformed into heat energy. This is why you feel hotter the longer you stand in the sun.
- Why do you think that is?
- Visible light itself is not hot but is transformed into heat as it is absorbed. This is why you can put your hand in front of the beam of a torch and not feel heat, but if you left your hand there for a while it would eventually become warm then hot as more light energy is absorbed and transformed into heat energy.
- Why do you think I chose to use a dark-coloured material for this demonstration?
- Dark colours get hotter more quickly.
- Why would dark colours get hotter more quickly?
- They absorb more light, so there is more light energy to transform into heat energy. Light colours reflect more light, so there is less light energy being absorbed to turn into heat?
- Where/when would you have to think about this in real life?
Discuss other applications of this phenomenon—for example, light bulbs getting hotter the longer they are turned on. You might also discuss problems this might create and solutions that have been/could be designed for it, with a focus on safety considerations. For example, workers using torches for long periods would have to take care the top of the torch doesn't get too hot and burn them. Stage actors can also become hot under stage lights.
If students need to make corrections or add additional details to the ray diagrams drawn on their Shadow masters Resource sheet, allow them time to do this.
Reflect on the lesson
You might:
- add new words and images to the word wall or glossary.
- add to the W and H sections of the TWLH chart.
- discuss how the learning from this lesson will be relevant to building light sculptures at the end of the sequence, including:
- consideration of the materials students are using in their sculpture, how much light it will let through, and the shadows that will be formed.
- the shapes of the shadows the sculpture might create.
- the umbra and penumbra of the shadows.
- how students might have to consider how the transformation of light into heat might impact their designs. Focus specifically on safety considerations here.
Umbra and penumbra
How are the umbra and penumbra formed?
If the light is coming from a broad source, for example, a torch, there will be two regions in the shadow called the ‘umbra’ and ‘penumbra’. The umbra is the region of the shadow (the darker part) where all of the light is blocked by the object. The penumbra (the lighter part) is the region of the shadow where only some of the light is blocked, that is, the light from only part of the source is blocked out.
If the light is coming from a broad source, for example, a torch, there will be two regions in the shadow called the ‘umbra’ and ‘penumbra’. The umbra is the region of the shadow (the darker part) where all of the light is blocked by the object. The penumbra (the lighter part) is the region of the shadow where only some of the light is blocked, that is, the light from only part of the source is blocked out.