Understanding the Eye

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Students understand how we are able to perceive light.

Big Idea

In this lesson, students learn how our eye uses light to be able to see color.

Engaging Them

10 minutes

I have a ball that flashes light when you bounce it. So, I got it out and really threw it hard against the floor and it didn't disappoint me. It flashed crazily and students "oohed" at the flashing. I heard a lot of, "How does it do that?" and "Cool." One student said, "The balls inside knock together and they flash." 

Instead of focusing on the "How does it work?", I asked them "How can you see it?" This question turned their thinking another direction. We talked about it a little, but I could tell they were baffled by my question. That was alright because this question sets them up to understand how their eye works.

My class doesn't have the advantage of dissecting a cow's eye yet, but as we transition into NGSS, that will add to our study of the eye. But I got to thinking about how kids perceive the eye and decided I would ask them to draw an eyeball as they think it works. After they sketched, I had them place their drawings around the room and we did a gallery walk. Student's talked to each other and were able to see the various ideas. After everyone had a chance to see the art work, we talked about our perceptions of how it works. From this discussion, I was able to assess what misconceptions needed to be addressed and what information I needed to focus on. 

I wrote the Driving Question on the whiteboard: How does the eye process light so that we can see? I asked them to come and sit on the floor while we would learn exactly how our eyes work. Who better to show us that, but Bill Nye?

Gathering the Facts

20 minutes

Student brought their notebooks and iPads as they sat in front of the SB to watch how Bill Nye would tackle explaining how the eye works. I had emailed the link to them so that they would have this clip for a reference. That way, as they gather their information, take notes and learn, they can refer back to the clip in case they can't keep up with notes or need to view it again to glean more facts. While the movie is only two minutes long, it moves quickly and not all of my students can capture the information that quickly. If you prefer to use the full clip, this will include a complete understanding of the eye. For the standard, the students must master understanding how light works within the eye. 

As students watched the video, they took notes in their science notebook on the right side of the note book. The left side was reserved for their observations in the next part of the investigation. 

We took a moment to discuss what they saw, but it was clear that a video simply would not be enough for them to understand how light works within the eye. We talked about the parts of the eye. I drew an eyeball on the whiteboard and noted each part that was responsible for us to see. They sketched the eyeball, labeled the cornea, pupil, iris, lens retina, optic nerve and the brain. I had them sketch a stick person upside down near the retina and then again, right side up in the brain.

To add to their understanding, the next part of the investigation would help them understand how the lens works as a magnifier and would refract the light. I asked them to go pick up their eyeball drawings and head with me into the lab with their notebooks and iPads for more fun!


20 minutes

Materials: Prepare enough ziplock bags for each student pair filled about 80% full of water. Zip them up really tight! 

Students entered the lab ready for more adventure. I asked them to find a partner and a seat. I brought around a baggy for each pair of students and told them to start looking through it at any object at a distance. I asked them to note any observations  in the left side of their notebooks. Then, I asked them to have their partner hold up their eyeball drawing and use the baggy to look at that from close up and then back away.  They wondered and tried to explain how it magnifies and I tried to help them connect it to their eye lens.  Students took turns explaining it  to one another. I asked them which part of the eye they thought the baggy modeled? They were hesitant to answer so I prodded them with some more supportive questioning. "What part of the eye would use light to change how the eye can process it?" The lens, of course!

We shared moments of what surprised them. I asked what their "aha" moments were! Students were really excited to share their ideas and thoughts. We discussed fish tanks and how it magnifies the fish.  This was a tough concept to apply to the lens of the eye, but I wanted to be sure to get them to connect the ideas and plant those seeds of understanding that we have models to help us understand scientific concepts, and in this case, how a part of our eye works. I continued to question them as I asked,  "What did you notice?"  

The discussion continued and led into how I sometimes the eye plays tricks on us. I wanted to know if they had ever seen anything that really wasn't what was there? This would help them understand how light plays a role in creating optical illusions. One example that came up was how the road sometimes looks like it has water on it and when you get to that spot there is no water. I explained that this was an optical illusion of a sort and it had a scientific explanation, but I wanted them to understand that sometimes light is part of playing tricks on what our brain thinks it is seeing.  

Wrapping Up

15 minutes

To wrap up this lesson and investigate some optical illusions, I played this short video clip of optical illusions. They were totally amazed at this video! ( It is awesome.) The samples of the optical illusions are very engaging and really work well with talking about how light has an influence on how we perceive these things. They were all wound up in amazement when they tried to count how many legs were on the objects. Some of them are really funny.The crazy engagement was a capstone for this fun lesson. 

After the movie, we closed our discussion with me asking if they had questions about the eye and how it is able to see. One student wanted to know how it can turn the image right side up so fast? My response? Isn't your body amazing? Your brain is designed to do split second and automatic responses. Sight is just one of many processes.

I had my students write a summarizing sentence in their notebooks about what they learned about how the eye processes light and any other "I wonder" questions they may still have.  I told them they could write the sentence starting with "I used to think that the eye..." and one more sentence that starts with, " I now know the eye..."  Communicating their understanding of how the lens works was a difficult concept.  Suddenly it clicked that when our lens don't work correctly, we wear glasses! This was a great connection!

I asked, "What did you learn?" to focus them and assess their understanding. They wanted to share their understanding  of the lens in almost every instance. This told me that the hands on experience surpassed simple showing them a video or copying terms from a text. I told them that we would continue to investigate how light travels and how that impacts how we see things.