Light, Sound and Waves

How do we see?

Teaching Guidance for 5-11 11-14 Supporting Physics Teaching

Common explanations

Wrong Track: The light is just there so that you can see things. If the light is on, you can see.

Wrong Track: You can see by looking at things. You just have to look at them.

Wrong Track: The light just helps your eye to see. It goes into your eye and then onto the thing you're looking at.

Right Lines: You are able to see as a result of light entering your eye. Light may come directly from a luminous source, or reflect off an object, or be scattered from particles and then enter the eye.

Pool of light

Thinking about the learning

For these pupils there is no sense of light travelling and entering the eye.

Active eye

Thinking about the learning

For these pupils seeing happens through light passing from the eye to the object. This model of seeing is reinforced by lots of expressions used in everyday talk. Thus we throw glances, give someone a dirty look, try to penetrate the fog with our eyes. All such expressions suggest that our eyes are active in sending out something.


Thinking about the learning

For these pupils seeing happens as a process of light passing to the eye, and then from the eye to the object, and then back from object to eye.

Challenging the ideas

Thinking about the learning

You need to help pupils understand that we see things as a result of light entering our eyes. For many pupils at the start of high school, this is not a problem. Nevertheless, there will be a range of ideas represented in the pupils that you teach and these are likely to include the previous three wrong track ideas.

Thinking about the teaching

How might you address some of these wrong track ideas in your teaching?

As outlined earlier, the pool of light way of thinking is very close to common-sense ways of talking about events. For example, if we use a torch to look for a pair of trainers in the cupboard under the stairs, there is a strong sense of the torch lighting up the space. Here, less thought is given to the torch sending out light, which reflects off objects and then enters the eye allowing us to see.

The idea that seeing depends on light entering the eye is further explored through activities in the teaching approaches.

The active eye model is best challenged through pupils experiencing complete darkness.

is formalised by Law of Reflection
can be exhibited by Progressive Wave
has the special case Total Internal Reflection
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