Light and Matter Unit

We watch a puzzling video of a person who can see their reflection in what seems to be a mirror. The person doesn’t see the people on the other side of the mirror, but those people can see through it like a window. We wonder how something can act like a mirror and window at the same time. We investigate the system using a box model that represents it (video). We develop an Initial Class Consensus Model, brainstorm related phenomena, and develop a Driving Question Board and an Ideas for Investigation chart. We figure out these things: 

• Some materials can be reflective and see-through at the same time.

• Whether the material is reflective or seethrough may be related to where there is a light.

In this lesson, we observe the one-way mirror in and out-of-the-box model. We move the flashlight to Room B, make both rooms light, and make both rooms dark. We figure out these things:

• When we change the location of light in the box system, the phenomenon reverses.

• Reflection happens on the side that is lit, while the side that is dark is see-through.

• The one-way mirror phenomenon is strongest when there is a difference in light between the rooms.

• Light travels in straight lines.

• For us to see an object, light must leave a light source, bounce off the object, and travel in a direct path to enter our eyes.

We know that the one-way mirror acts like a mirror in a brightly lit room and acts like a window in a dark room. To figure out why it behaves this way, we compare what happens when light shines on the one-way mirror, a pane of glass, and a regular mirror. We record initial observations and then use a light meter to measure the amount of light transmitted through and reflected off each of those materials. We use a tool to develop an experimental question and then plan the investigation. We document our observations and analyze data to figure out what happens when light shines on the one-way mirror. We figure out these things:

• Light travels in straight lines. 

• When light shines on an object, it is reflected (bounces off), transmitted (passes through), or some combination of these, depending on the object’s material.

We wonder how similar amounts of light transmit through and reflect off the one-way mirror. We think it has something to do with how the one-way mirror is made. We read more about regular mirrors and one-way mirrors and find out that regular mirrors have a thick layer of silver on the glass, and one-way mirrors have a thin layer of silver embedded in a plastic film on the glass. We modify a model to explain what happens when light shines on the different structures in each material. We figure out these things:

• A material can have different structures, even at a microscale, that cause different amounts of light to transmit through or reflect off of it.

In this lesson, we revisit the anchoring phenomenon and model interactions between light, people, and the one-way mirror to explain why the music student and the adults all see the music student. We realize that a little light reflects off the adults and enters the student’s eyes, which makes us wonder why the student doesn’t see the adults. We figure out these things:

• When light reflects off the music student and travels to the one-way mirror, about half of the light reflects off the silver structures back to the student’s eyes and the other half transmits through the transparent parts to the adult’s eyes.

• The light that transmits through the oneway mirror reflects off the adults and travels to the one-way mirror. About half of that light reflects off the silver structures back to the adult’s eyes and the other half transmits through the transparent parts to the student’s eyes.

In this lesson, we know that light has reflected off the adults and enters the student’s eyes. We wonder why the student can’t see them. To figure this out, we obtain more information about what happens when light enters the eye (video). We model how light inputs transform into signals that the brain processes to tell us what we see. We think about experiences from our everyday lives to help us explain why we only see some inputs of light better than other inputs. We figure out:

• Light changes direction (refracts) when it travels between different transparent materials.

• When a light input is detected by sense receptors in our eye, it is turned into a signal that travels along the optic nerve to the brain, which processes it into what we see.

• When there are multiple inputs, the brain responds to the strongest signal. 

In this lesson, we review the class models from Lessons 5 and 6, the class science ideas list, and our individual Progress Trackers. As a class, we develop a written explanation to answer the question: Why do the adults see the music student? We individually draft an explanation to answer the question: Why does the music student see themself but not the adults? We self-assess our explanations and give and receive peer feedback on them. We then revise a final explanation. We figure out these ideas:

• The music student sees themself because light reflects off the music student to the oneway mirror and reflects back to their eye. This light input is the strongest signal that is processed by their brain.

• The adults see the music student because light reflects off the music student to the oneway mirror and transmits through the mirror to their eyes. This light input is the strongest signal that is processed by their brains.

• The music student can’t see the adults and they can’t see their reflection because the light input from those objects are weaker and the brain doesn’t respond to them.

We investigate the best light conditions for the oneway mirror phenomenon to occur and decide the effect is greatest when there is a large difference in light on both sides of the material. We use this idea to investigate related phenomena. We conclude that other materials, like glass, can act like one-way mirrors in situations in which there is a similar light differential on either side of the material. We use our model and science ideas to demonstrate what we have learned on an assessment. We revisit the DQB to document the questions we have answered in the unit and to reflect on our learning. We figure out these ideas:

• Differences in light on either side of an object or material can cause us to see different things when looking at the same object or material.

• The brighter or more prominent an object appears, the more light that reaches our eyes from the object.