Construct a Scientific Explanation Based on Evidence
Pencil in Water Phenomenon
Feature
3
o Student articulates a statement that relates the given phenomenon to a scientific idea.
o That light waves are refracted as they enter the water because light waves travel at different rates depending on
the material in which they travel.
Articulating
o We can see the pencil because the light waves are reflected off of the pencil and enter our eye.
the
o Student uses evidence and reasoning to construct a scientific explanation for the given phenomenon.
explanation
o Appropriate evidence would include the information from our investigation with the transparent, acrylic prism
of
(the light entering the prism traveled in a straight line, except at the surface of the transparent prism) and the
phenomena
reading selection (light waves change their speed based on the density of the material in which they pass) on
refraction.
o Supporting evidence for the reflection of light off the pencil would include the investigation on reflection (the
path that light travels as straight lines)
o Student identifies and describes evidence (e.g., from student’s own investigations, observations, reading materials,
archived data) necessary for constructing the explanation, including:
o In the reflection activity we discovered light travels in a straight line and that it is reflected off of some materials.
Evidence
o In the reading selection on reflection, we learned that reflection is one way that light can interact with matter.
o In the refraction lab, we discovered that light will change direction when it enters a transparent material
o In the refraction reading we learned that when light changes direction in a transparent materials, the light wave is
slowing down and that bending light is called refraction.
o Students use reasoning, along with the assumption that theories and laws that describe the natural world operate
today as they did in the past and will continue to do so in the future, to connect evidence and support an
explanation for a phenomenon. Students describe their chain of reasoning that includes:
Reasoning
o Light travels in a straight line. When light shines on an object, it is reflected or transmitted through the object,
depending on the object’s material.
o The path light travels can be traced as straight lines, except at surfaces between different transparent materials
where the path of light bends.
Text in bold is from the evidence statements that are based on the science and engineering practice of Constructing Explanations.
Construct a Scientific Explanation Based on Evidence
Pencil in Water Phenomenon
Possible response:
In image A the pencil appears straight because the cup only has air in it. In our investigation with the light box, we observed that
light travels in a straight line and it reflects off of shiny surfaces, like a mirror. In the reading on reflection, we learned that light always
travels in a straight line and will reflect off of smooth surfaces at the same angle that it hits. The light in Image A travels from its source
and is reflected off of the pencil and enters our eye so we are able to see it. Since the light is always traveling through the air, the
image of the pencil does not change.
In image B, the light leaves its source and then comes in contact with another transparent substance (the water in the cup).
Because the water is a different substance, the path of the light wave, changes speed and bends. When the light is reflected off the
pencil it is now at a different angle and the pencil appears bent when it enters our eye. In the lab with the transparent prism, we
observed that light enters the transparent prism and depending upon the angle that it enter, the light will bend (change speed) and
exit the prism at a different angle as demonstrated by the three different colored lines. We read that this bending of light is called
refraction and is one of the ways that light can interact with matter. The pencil looks different in image B because the light is refracted
when it enters the water.