Exploring Light/Lesson

Light dark and somewhere in between?

Learning experiences covered

• Number and counting.
• Quantity.
• Collecting data and drawing tables of data.
• Describing things by number.

You will need:

• A datalogger with a light sensor (attached to the computer linked to your interactive whiteboard, projector or other large display),
• Software that shows the product of the datalogger as bar charts or numbers (meters),
• A good light source (class lights, well lit window, torch),
• A selection of objects that:
  

- block light

- let light through clearly

- let light through to some extent

- let light through but colour it (e.g. A4 sheets of card, paper, plain and coloured translucent film, different fabrics, etc.)

Suggested method

Ask the children to talk about what lets light through and what does not. See if they remember the words that describe letting light through, blocking light, disturbing light changing colour of light. Ask them in learning groups to make lists of 5 things (of each) that let light through without change (transparent), distort the light or what you see (translucent), don’t let through (opaque). Create a master list and check the grouping is correct, challenge any that are in wrong place to see why.

Using the logger

1. Set the software to show numbers as a set of blocks or bar chart.
2. Check they understand that big numbers or longer bars means more light, less dark and smaller numbers and shorter bars means less light and more dark.
3. Measure the light without any blocks or things in the way. Snap the data to show it on the software as a bar. This is your reference (control, as science describes it) point against which all others are compared.
4. Place an object between the light and the sensor in the logger. Snap the value.
5. Place a block over the sensor, use the snap to record the data. Compare the open light, shaded and blocked bars.
6. Ask them to think of the brightness or darkness of the light as a number not a word description. For example, “I know this is bright because it shows 2000lx”, “I know this is dark as it only shows 100lx”. We are trying to build up the idea of describing by numbers.
7. Now a base for comparison has been created, repeat with other things you have selected.

- Does the colour make difference?

- Does the size of any dark patch make a difference?

- Does the opaqueness of the shadow maker make a difference?

- If you use transparent thing does the colour make difference to the amount of light?

8. Just explore, keep noting down the discoveries, is there a pattern? Are we starting to see the “shadowness” of shadow? Or is it still too difficult?
If you have access to enough transparent filters of colour, get the class to look through them and put them in order of brightness! Some colours appear much brighter than others, yellows often seem brighter than reds, blues can appear dull. As a diversion, ask them about how the colour makes them feel, some colours like reds are supposed to make things look warm, while blues make it feel cold!
You can use coloured paper presentation folders (the ones you clip into a file folder). Ask them to place over work and see if helps reading? Some people find bright white paper too bright to read off (we are getting close to dyslexia testing here, so a bit of awareness is required). They may already be aware of colour combinations that make reading difficult e.g. bright yellow on bright white!

Teacher’s notes

Key Questions

1. What is light and what is dark?
2. Can we use numbers to describe something as well as words?
3. What else changes light?
4. How do you describe things that change how you see light?
5. What is colour?

In previous work we have looked at dark, light and shadows. We have been saying in our story that:

• we can define dark and light,
• we can say something is brighter or darker than something else and give a number to support,
• we can define a shadow,
• we can use numbers to describe to others what we see, but they may not.

Our next part of the story is, what about the graduations between dark and light? How can we describe to others how much light or dark we have seen?

Coloured filters should give lower light readings, this is clue that some light has been blocked by the filter and that only a small part has passed through. The part that passes through is what we see as colour. White light is a mixture of many colours.

A reminder of the terms used to describe the ability of objects to let light through them.

• Opaque = Lets no light through, a brick wall is opaque.
• Transparent = lets light through without changing it, a clear glass window is transparent. If we put colour into it we make a filter, but transparent will do.
• Translucent = lets light through but distorts what you see, a frosted glass window to a bathroom is translucent.
• Filter = blocks parts of light but lets parts through without changing. The blocking removes some light and produces colour.