What is the ISLE approach?
ISLE (Investigative Science Learning Environment) as a philosophical approach to learning, has two core intentionalities: 1. We want students to learn physics by thinking like physicists; by engaging in knowledge-generating activities that mimic the actual practices of physics and using the reasoning tools that physicists use when constructing and applying knowledge. 2. The way in which students learn physics should enhance their well-being.
The Investigative Science Learning Environment (ISLE) is an holistic interactive-engagement approach to learning and teaching physics that has a goal of engaging students in learning physics by following processes similar to those that physicists use while constructing and applying new knowledge. The approach includes all aspects of students learning physics such as constructing, testing and applying new ideas through experimentation and reasoning, solving problems and of class organization including assessment and grading policies.
To have an image of how the process works, we show a simple example here.
In order to help the reader understand the logical progression of the ISLE approach, let’s use an example of students constructing an understanding of how extended objects emit light.
Preparation: What do we need to see and how does light travel? Some people still have the idea that our eyes emit light rays that reached the object, go around it and return to their eyes, telling them about the object. Thus, many people think that if they sit in a dark room for a long time they will eventually be able to see. To help students develop the idea that we need a source of light to be able to see objects, the teacher invites students to a completely dark room, lets them sit for some time and then asks them what they can see. All students agree that they cannot see anything. This is their first observational experiment. It leads to a question – what do we need to see? Students come up with an answer: we need a source of light. But do we see light? And how does light travel?
To help students answer these two questions: (1) how does light travel? and (2) do we see light? We invite them to observe a laser beam in a dark room. They all see the bright spot but no one can see the beam itself. Students work in groups and devise an explanation that they see the bright spot as light bounces off it and comes back to their eyes. To be able to see how light travels students suggest putting paper in the way or spray water between the laser and the screen. Now they all can see the path. What made the path visible? Students quickly come up with an answer that they can see the path because light bounces off tiny droplets and comes into our eyes. They see that the light beam follows a straight line. Now the teacher can give a name for the line which the beam follows– “a ray”. Light ray is a model of a very narrow light beam. The students learn a key representational tool of geometrical optics: A straight line drawn with a ruler that represents a beam of light.
Now the students are ready to figure out how extended objects emit light.
Observational experiment and development of models: Every group of students has a frosted bulb. They turn it on in a dark room and watch the walls and the ceiling. They are lit. Now there is a question: How does the bulb emit light rays? Students work in groups to devise possible models. They usually devise two models: each point of the bulb emits one ray pointing radially outward from the bulb, or each point of the bulb emits multiple rays in all directions.
Testing of the models: Now the students need to decide what to do about those models – which one is not right? Here the students employ hypothetico deductive reasoning. To test the models that they invent, they need to design experiments whose outcomes they can predict using the models they proposed using the following reasoning chain: If _______ model (hypothesis) is correct and I do __________(testing experiment) , then __________(predicted outcome based on the model) should happen. The progression of their thought (based on the observations of many student groups) is shown in the table below.
| Testing Experiment | Prediction based on one-ray Model | Prediction based on multiple ray model | Outcome | |
| 1 |  Turn on a lightbulb and place a pencil close to the wall, between the bulb and the wall |  Dark, sharp shadow behind the pencil |  Dark shadow behind the pencil |  Dark sharp shadow on the wall |
| 2 |  Turn on a lightbulb and place a pencil closer to the bulb between the bulb and the wall. |  Dark, sharp shadow behind the pencil |  Light, fuzzy shadow on the wall |  Light, fuzzy shadow on the wall |
| 3 |  Cover the bulb with aluminum foil and poke a hole in the part of the foil facing the wall. Turn the bulb on. |  Small spot on the wall directly in front of the hole. |  Whole wall will be dimly lit. |  The whole wall is dimly lit. |
Testing experiments in the table reject the one-ray model and support the multiple-ray model. Through experimentation, students have established a key idea of light studies: each point on the surface of the bulb acts as a point-like source of light and sends an infinite number of rays in all directions.
Application: Now the students can apply this ides in a new situation. An example of a problem is to predict the outcome of the pinhole camera experiment and then to design the pinhole camera by themselves. They can make a simple pinhole camera using cardboard box. To reduce bright ambient light they can use a cellphone camera to record images and videos that form on the screen inside the closed pinhole camera. Watching the recorded upside-down image of the objects that students predicted earlier creates feeling of success and excitement – even if students saw the pinhole camera before.
The above progression shows that students construct the model of extended objects emitting light (crucial for understanding how mirrors and lenses form images) following a path from observing simple experiments to devising multiple models explaining them, testing the models and applying them for practical purposes. This sequence represents the logical progression of the ISLE approach This process summarized in the figure below. It is by no means linear and prescribed. Note that while the arrows on the diagram represent a progression of logical steps, at any step one can go back and revisit the previous step or examine the assumptions. In the following section we will discuss how to practically implement the ISLE approach.