The pedagogy of making: Pinhole camera

Inviting students to ‘make’ simple models of scientific instruments from scratch has many advantages. Constructing and analysing how and why these models work allows students to experience what it means to think like a scientist. Using inexpensive, local, and easily available materials to make these models strengthens their creativity, ability to improvise, and the ability to learn from failures. Understanding the role of different components of the model and playing with different variables deepen students’ engagement with related concepts. Making experiences can also help students develop many important science skills, like the ability to manipulate or change a model to expose its properties, observe cause-and-effect relationships and correlational changes in different variables, and identify the limitations of their inferences. Students retain the knowledge and skills they gain from such making experiences for longer durations. Regular opportunities of this kind can help students develop into independent learners.

It is to encourage such making experiences in the classroom that science textbooks for the middle stage include step-by-step procedures for constructing instruments and models that support understanding of related curricular concepts. Often, teachers expect their students to read, understand, and follow these procedures on their own and as exactly as possible. While students may develop some technical proficiency and conceptual understanding from this mechanical repetition, they need to have the opportunity to use and develop their creative and critical thinking skills. To use the pedagogy of making most effectively in the classroom, teachers need to:

• Encourage students to modify the procedures shared in the textbook to match the materials and time available to them.
• Allow students to operate their models to understand their working principles.
• Ask students probing questions about their observations and findings to lead them towards new areas of inquiry.

Some textbook procedures can be quite complex, involving many steps and precautions. In such cases, students may depend on their teachers for step-by-step guidance and support. Even if they try to follow the procedure by themselves, it can take so much time, energy, and attention that students may be unable to focus on manipulating the different components and variables of the model. A creative science teacher can resolve this issue and bring their students’ focus back towards the learning objectives of the session by simplifying the procedure and requirements for model making. One example of this can be seen in the procedure for constructing a pinhole camera included in the Grade VI curriculum (see Box 1).

Box 1. Pinhole cameras in the Grade VI curriculum:

A pinhole camera is an optical instrument that forms an image without using a mirror or a lens. In its most common form, it consists of a light-proof hollow box with a tiny aperture (pinhole) on one side and a translucent screen on the opposite side. When students turn the aperture side of the box towards an illuminated object, they will see a real but inverted image of the object projected on the screen (see Fig. 1).¹ The construction of a pinhole camera is included in Chapter 8 (‘Light, Shadows, and Reflections’) of the Grade VI science textbook (NCERT, 2023-2024).² This chapter describes the property of light to travel in a straight line in a transparent medium. Called the rectilinear propagation of light, this property can be used to explain many real-world phenomena like eclipses and the formation of shadows. It now appears in Chapter 11 (‘Light’) of the Grade VII science textbook (NCERT, 2024-2025).³

While this property is often taught as a fact to be memorised by students, the National Curriculum Framework for School Education (NCF-SE) 2023 recommends that: “…simply stating the rectilinear propagation of light is insufficient… To extend the example of rectilinear propagation of light, students can observe this through the…simple manipulation of cardboard sheets with small holes in front of a candle, or using a pinhole camera/ periscope made in the classroom”.^4,5 A related learning outcome for Grade VI science is that: “The learner constructs models using materials from surroundings and explains their working, e.g., pinhole camera, periscope, electric torch, etc”.⁶

Making a pinhole camera

I invited Grade VI students of an upper primary government school at Uttarkashi to make and manipulate their own pinhole cameras (see Activity Sheet: Make your own Pinhole Camera). This was the pedagogical approach I used:

Step 1: I started the activity by showing students a pinhole camera I had constructed using just a disposable paper cup and a piece of butter paper large enough to cover the open end of the cup. I had pierced the closed end of the cup with a pin to make a hole through which light from an illuminated object could enter the cup. The butter paper acted as a screen on which the image of the object is projected. I encouraged students to handle the camera themselves and see if they could guess the materials required to construct it. Once they had named the materials they could see, I lit a candle, turned the camera surface with the pinhole towards the flame, and asked students to observe the screen of the camera. Students shared that they could see an inverted image of the candle flame. I dismantled the camera and showed the students each of its parts. The main objective of this exercise was for students to understand that any opaque surface with a pinhole can be used to filter light and any translucent surface can be used as a screen to project the image of an illuminated object.

Step 2: When my students expressed the wish to construct their own cameras, I invited them to take building materials from a box kept on the teacher’s table. This included paper cups, cutters, pieces of butter paper, glue, tape, etc. As students returned to their tables with these materials and began assembling their models, I walked around the class observing their work.

Many students found it difficult to attach the butter paper to the cup without wrinkling or tearing it. In such cases, I encouraged them to ask a friend for help. At first, students used a rubber band to secure the paper to the cup. But, we observed, that screens secured in this way showed wrinkling with repeated use. So I recommended that students use glue to permanently secure the ends of the butter paper to the cup. After all the students in the class had constructed their own cameras, I invited them to check if their models worked. I lit a candle on the teacher’s table and students brought their cameras to the table to see the image formed on their screens.

Encouraging deeper inquiry and discussion

One of the first student cameras to be tested produced a blurred image. Without needing any instruction, the student who had constructed it began to adjust the distance of their camera from the candle—moving the camera first a bit closer, then a bit farther away from the flame. Through this process of minor adjustments, they were able to arrive at the distance at which their image was sharpest. Another student observed that changing the distance between the camera and the flame changed the size of the image too. Each of the other students tried this focusing activity for themselves. Through these experiments, they concluded that the closer the aperture of the camera is to an illuminated object, the sharper is its image on the screen.

Some students struggled more than others to get a clear image of the flame. I asked these students to compare their cameras with those of their classmates: Could they see any clear differences in construction? One of the differences we observed was in the size of the hole through which light enters. Some of my students had pierced the bottom of their cups with the tip of a ballpoint pen rather than a needle. This led students to conclude that the smaller the size of the hole in a pinhole camera, the sharper the image it produced. My next question was: What would I see on the screen of my camera if I made a smaller second hole (with a pin) near the larger first one (with the tip of a ballpoint pen)? Some of my students decided to try this out and were surprised to see two inverted images of the flame on their screens. This triggered the curiosity of other students, who immediately started poking multiple holes in the bottom of their own cups. They spent some very exciting moments comparing the patterns and orientations of the multiple images this produced on their screens. To bring my students’ attention back to the clarity of their images, I asked if it would change by darkening the room. Since the students were not sure of what effect this would have, I encouraged them to test it. When we closed the windows and switched off the one light bulb in the classroom, the images on their camera screens became a lot clearer. When I asked why this happened, some students suggested that darkening the room may have helped ensure that most of the light that entered the camera came from the flame. I pointed out that we had already ensured this by blackening the bottom and the sides of the cup. After some discussion, the students concluded that the less light from the environment the screen is exposed to, the sharper the image on it.

I asked my students if we could modify the design of the camera to reduce the amount of light from the environment that the screen is exposed to. One student suggested blackening the screen. I agreed that this would meet our aim. But, I asked, how would it affect the image of the flame on the screen? Seeing that my students did not know how to respond to this question, I asked if they could tell me why we were using butter paper for the screen. Could the screen be made from other material too? Since this too was met with silence, I asked students to suggest any other material that we could try using as a screen. My only condition was that the materials needed to be inexpensive and easy to find. As the students shared their suggestions, I listed them on the class board: Oiled paper, plain white paper, cloth, and polythene. I added blackened paper to this list and invited the class to try out each of these alternatives. Working in groups, the students constructed 5 different models of the camera. On testing these models, they discovered that images of the flame were visible on screens made of white butter paper and oil paper, but not on those made of polythene, white paper, and blackened oil paper. I asked if they could explain this observation. After some discussion, the students suggested that a blackened or opaque screen (like one made from white paper) blocked light from the candle from reaching our eyes. In contrast, a transparent screen (like one made from polythene) allowed the light to pass through without forming an image.

I brought the discussion back to the question we started with: Could we modify the design of the camera to reduce the light from the environment that the screen is exposed to? One of my students suggested covering the screen with something like a paper wall. Other students pointed out that the wall may help cut down light from the environment, but it would also obstruct our view of the image on the screen. Another student rolled a strip of black chart paper into a hollow pipe like structure and asked if we could use this to view the image on the screen. A third student backed the idea of a paper wall with one change: We cut out a small window through which we could view the screen. Discussion on both these modifications led to the decision to combine them. We blackened the outer surfaces of a second paper cup and cut out a small piece of paper from its bottom. The mouth of this cup was taped to that of the pinhole camera (see Fig. 2). When students tested the new model, they observed that the image produced by it in an undarkened room was as clear as the image produced by the older model in a darkened room. At the end of the session, I encouraged my students to take their cameras back home and use them to see images of different illuminated objects, like trees, animals, other human beings, the Moon, etc.

Parting thoughts

Making experiences offer students the opportunity to learn science in the process of doing it. For example, teachers can connect student observations and experiences of making a pinhole camera with textbook concepts of rectilinear propagation of light, the classification of objects (into transparent, translucent, and opaque) based on how much light passes through them, image formation in different types of cameras, and the properties of these images. But, to do this, it may not be enough to ask students to mechanically follow complicated procedures from the school textbook. Instead, teachers need to use their own creativity to build simpler models (preferably with fewer and less expensive materials) that students can break down and reassemble by themselves without needing too much help or guidance. Teachers also play an important role in asking questions that encourage students to experiment with the materials, construction, and working of these models. These can offer students the chance to develop analytical, reasoning, and critical thinking skills. Such making experiences can go beyond offering connections to curricular concepts by helping students relate to the process of science through their creativity and curiosity.