Children in infant and junior classes will identify different light sources, explore the effects of light on materials, identify materials that are transparent or opaque, and experiment with shadows and reflections. Children will come to appreciate that they see objects and different colours because of light.
In the middle and senior classes pupils will distinguish between natural and artificial sources of light and will explore how white light is made up of many different colours. Children will investigate how light rays change direction as they pass through water and learn that this process is called refraction. Through designing and making activities pupils will develop a greater understanding of how mirrors and other shiny surfaces can change the direction of light and will explore how lenses are used to make things look bigger (magnified) or smaller.
Safety
When planning a unit of work on light the teacher will ensure that the children are aware of and adhere to the following safety procedures:
- children should not look at the sun or at very bright beams of light, such as projector beams
- plastic mirrors should be used for investigations, and children should avoid using glass mirrors
- pupils should never look at the sun through lenses
- children should be made aware of the dangers of sunburn.
Lessons on light energy present opportunities for teachers to instil in children the need to protect their eyes.
Introducing light and colour in the early years
In the infant and junior classes the concepts of light energy and colour should be integrated with other aspects of the curriculum.
Colour
Children in junior and senior infants should learn to identify and name different colours. Activities that develop an appreciation of light, colour and different shades of colour will involve the pupils in
- collecting objects and materials for colour tables. For instance, a 'red table' will include many items to represent the different shades of one colour that can be found. The children can arrange the items in order, from the darkest to the lightest. This will develop an awareness of variation within one colour
- making collections of seasonal colours throughout the year. Children can display different-coloured items found in the environment during the different seasons, such as the brown, gold, red and yellow colours of falling leaves and various fruits and seeds
- exploring colours in the street, village or locality. Children can go on 'colour walks' during the different seasons and observe
- the colours that make the best signs
- signs that can be seen at night
- the colours that are associated with danger, for example in traffic lights and pedestrian crossings
- the colours used for different elements of street furniture (litter bins, street lights, letter boxes, traffic lights and hydrant points)
- colours that blend into the background and are hard to see.
The children might experiment and devise tests to establish the colours that are more visible in daylight, in the school yard and in the artificial light of the classroom. They might test the following ideas:
- Which colour of coat should the crossing warden wear?
- Which colours are the best for a road sign?
Exploring light and shadows
As well as developing an awareness of different colours and their use in the environment, it is important for children during the infant and junior classes to become aware of a variety of sources of light. Work on the topic of light and shadows will also increase their awareness that a variety of objects, such as torches, lamps and bulbs, give artificial light. The children will come to realise that some objects, such as their bodies, trees and cars, block out light and create shadows. Work on light and shadows can be undertaken indoors and outdoors.
Exemplar 22 illustrates an approach to the selection of content for a unit of work on light and shadows, possible methods of organisation and ideas for investigations and experiments.
Exploring light energy in the junior classes
In first and second classes children should recognise that the most important source of light energy for the Earth is the sun. Children should be encouraged to think about their own experiences of light and heat from the sun, for example sunburn, shadows, sundials and growing plants. This work should link with activities in the strand unit 'Earth in space' in the geography curriculum.
Pupils should know that light comes from different sources. The children can make a collection of these light sources so that they can be examined at first hand. They should be made aware that they can see objects because the light that shines on the object is reflected into their eyes. It might prove useful for children to imagine themselves in a dark cupboard. When the door is open, light enters and they are able to see. As the door is closed, light is excluded and their vision is reduced.
Exploring the effects of light and materials
This work should be an extension of the initial explorations of making shadows that were covered in the infant classes.
Children will explore how different materials can be sorted into sets -- those that allow light through and those that do not. A variety of materials, such as glass, Cellophane, clear plastic, frosted glass, greaseproof paper, plastic sweet wrappers, paper and water, should be available to the children for experiment. Children in the junior classes may be able to identify two types of materials. Things through which light passes can be described as transparent; materials that do not allow light to pass through are opaque and will form shadows Children in third and fourth classes may identify a third set of materials: translucent materials, such as frosted glass and waxed paper, which allow light to pass through but only in a blurred way. Once the children understand how materials can be classified as transparent, translucent and opaque they should explore the school and its environs for samples of each type.
This strand unit provides many opportunities for designing and making with materials that are transparent, opaque and translucent. The exemplars in the science curriculum (pages 31 and 46) provide children with contexts within which the properties of materials used for making common objects such as lampshades, sunshades and glasshouses are examined. Children can discuss how to test the properties of each material. They might consider thatthe material used for glasshouses should be both transparent and waterproof. They might test different transparent materials to establish which one does not scratch easily. Such a material may be used to make a pair of sun shades. Samples of lampshades from children's homes may be examined and their properties assessed. The children can then design their own lampshade, using their own criteria and materials.
Investigating colours in sunlight -- middle and senior classes
By the end of fourth class children should know that white light can be split into a range of colours, known as a spectrum. The children can use a slide projector and prism to cast a large spectrum on a wall. They can identify the colours and the order in which they appear on white paper or the screen. Other ways for children to see the spectrum are
- to place a plastic ruler in the sunlight and watch the spectrum as it appears on the ceiling or wall
- to blow bubbles
- to place a mirror in a shallow container of water in sunlight.
The white rays of sunlight fall on drops of rain, which act in a similar way as the prism to form a rainbow. Children can experiment to make a rainbow.
Mixing coloured light
The children should try mixing the primary colours of light. Three torches should be covered with red, blue and green filters and shone onto a white screen or piece of paper. The children will observe that different colour combinations occur. Green and blue light will combine to make cyan (bluegreen); blue and red light make magenta (purple-red); and green andred light make yellow. Together the red, blue and green light beams should give white light, but only if the colours are pure and are projected at the same intensity. The process of mixing the primary colours of paint is different from mixing the primary colours of light; colour paints have a different set of primary colours.
Children should investigate what happens when they look at flowers, crayons and other coloured objects through different-coloured filters, and should record the results.
EXEMPLAR 22 - Light and shadows (infant and junior classes)
Reflection of light from shiny surfaces
Children in the middle and senior classes will investigate that mirrors and other shiny surfaces can change the direction of light. A period of unstructured exploration should be planned so that the children can try bouncing sunlight on walls or playing 'light spot tag'. These activities should help children to realise that mirrors reflect light. Children can bounce a beam of light from a torch or projector off a mirror and onto another surface. Further investigations of the effects of bouncing light beams using two or more mirrors can be carried out. Designing and making a simple periscope using mirrors will support this work.
Through exploration, children will discover that mirrors reverse images. Games where they have to make themirror image perform an action, such as blinking the left eye or touching the right ear, can be played. Work with mirrors will enable teachers to introduce the concept of symmetry. The children can be given half a picture, for example a butterfly, and asked to use a mirror to complete it. An investigation of the presence or absence of mirror symmetry in letters of the alphabet can also be undertaken. The children can first predict the letters that they consider to be symmetrical. They may come to conclude that some letters -- X, O, I and H -- have both horizontal and vertical lines of symmetry.
Materials and light: light refraction
Children should explore what happens to light as it travels through air, water and glass. A collection of transparent glass and plastic objects, such as bottles, glasses and fishbowls, should be available to the children. They will observe that when a pencil is placed in a glass of water it will appear broken at the boundary between the water and air. The children can predict how the pencil will appear in different containers. Compare how straight-sided and curved containers affect the appearance of the pencil.
Lenses
Children can explore how objects can be magnified using simple hand lenses. They should also observe how common objects such as drops of water, clear marbles and some water-filled containers can be used as magnifiers. They will discover that any clear, curved transparent material acts like a lens. Light rays that pass through the material are bent. This may cause objects viewed through the lens to appear magnified or reduced. The magnifying power of two different improvised lenses, such as a narrow jar of water and a wide jar of water, can be compared.