Science on This Day: November 18 | The Chemistry of Photography and the Biology of Vision
Science helps us understand how we record the world and how we experience it. A photograph can preserve a moment long after it has passed, while our eyes convert incoming light into signals that the brain interprets as colour, shape and movement. Both processes depend on light, but the chemistry and biology behind them are very different.
November 18 connects these ideas through the birth of Louis Daguerre in 1787 and the birth of scientist George Wald in 1906. Their stories offer useful classroom links between chemistry, biology, physics and technology, showing students how investigations into light have helped us understand both the world outside us and the way we see it.
Louis Daguerre: the chemistry behind early photography
Louis Daguerre was born on November 18, 1787. He became known for developing the daguerreotype, an early photographic process that helped make photography practical during the nineteenth century. Before photography became widely available, recording a person’s appearance or a landscape generally required an artist, a drawing or a painting.
Photography offered a new way to create detailed images of the world.
A daguerreotype was made using a highly polished, silver-coated copper plate. The plate was treated with chemicals to make its surface sensitive to light, exposed in a camera, and then processed to reveal an image. The process involved light-sensitive silver compounds and chemical treatment. It was not simply a matter of light leaving a permanent mark on a piece of metal.
This is a useful example of how scientific knowledge can turn an observation into a technology. People had long understood that light could create visible effects, but developing a practical photographic method required experimentation with materials, exposure times and chemical processes. Daguerre’s work helped establish photography as an important tool for portraiture, documentation and scientific observation.
Photography also changed science itself. Images could preserve details that might otherwise be difficult to describe or reproduce. Researchers could document specimens, landscapes, astronomical observations and changes over time. Modern digital cameras work differently from daguerreotypes, but both rely on detecting light and converting its effects into a record.
A classroom connection: how does light make an image?
Students can investigate the relationship between light and images without reproducing historical photographic chemistry. Ask them to compare a photograph taken in bright sunlight with one taken in a dim room. What changes? They might notice differences in brightness, clarity, colour or the amount of time needed to capture an image.
A discussion can then explore what a camera needs to control: the amount of light entering, the time light is collected, and the way the image is recorded. Students can compare a film camera, which relies on light-sensitive chemistry, with a digital camera, which uses an electronic sensor.
For a more inquiry-focused lesson, give students the question: “What makes a photograph a useful scientific record?” They could consider how lighting, scale, focus, camera position and image editing might affect the evidence a photograph provides. A photograph can be informative, but it can also be misleading if important context is missing.
This activity connects physics and chemistry to media literacy and scientific evidence. It is also an opportunity to discuss how technologies change what scientists can observe and share.
For further classroom activities across science disciplines, explore The Teaching Astrophysicist’s resource store, which includes both free and paid resources.
George Wald: understanding the chemistry of vision
On November 18, 1906, American biochemist George Wald was born. His research helped explain the chemistry of vision, including the role of vitamin A and light-sensitive pigments in the eye. He received the Nobel Prize in Physiology or Medicine in 1967 for discoveries concerning the primary physiological and chemical visual processes in the eye.
Vision begins when light enters the eye and reaches the retina, a layer of light-sensitive tissue at the back of the eyeball. The retina contains photoreceptor cells called rods and cones. Rods are particularly important for vision in dim conditions, while cones support colour vision and detailed vision in brighter light.
Inside these cells are light-sensitive molecules. When light is absorbed, a molecule in a visual pigment changes shape, triggering a chain of chemical and electrical events. The resulting signals travel through nerve cells and along the optic nerve to the brain, where information is processed into what we experience as sight.
Wald’s work helped scientists understand that vision is not just a passive process in which the eye receives an image. It depends on chemical reactions that respond to light. Vitamin A is important because the body uses it to make a component of the light-sensitive molecules involved in vision. A lack of vitamin A can therefore cause serious vision problems.
This is a useful way to connect biology to chemistry. Students often learn about the eye by labelling its structures, but the chemistry explains how those structures function. The retina is not simply a screen. It is living tissue that converts light into signals the nervous system can use.
A classroom connection: how do our eyes respond to light?
Begin by asking students why it is difficult to see when they first enter a dark room from bright sunlight. As their eyes adapt, their ability to see in dim conditions improves. This provides a starting point for discussing how the visual system responds to different light levels.
Students can compare the roles of rods and cones, then develop a simple explanation linking light detection, chemical changes, nerve signals and the brain. They could create a flow diagram showing how light reflected from an object eventually contributes to the experience of seeing that object.
Another useful question is why the same object may look different under different lighting. Students can investigate how the light source affects the wavelengths reaching an object and then entering the eye. This can lead to discussion of colour, reflection and the brain’s
interpretation of visual information.
For older students, extend the discussion to the difference between detecting light and interpreting it. The eyes collect information, but perception also depends on how the brain processes that information. Optical illusions can provide examples of how perception does not always match a simple measurement of the physical world.
The Nobel Prize website provides a helpful starting point for learning about Wald’s research and its significance: George Wald’s Nobel Prize facts.
Three ways to connect photography, vision and light
Daguerre’s work and Wald’s research make a natural pairing because both concern the relationship between light and the recording of information. A camera uses materials and sensors to capture an image; the eye uses photoreceptors and neural pathways to produce visual information for the brain. Comparing the two can help students identify similarities without assuming that the eye works exactly like a camera.
For a short cross-curricular task, ask students to compare the two systems. Both require light, and both respond to information from the environment. However, a camera records an image through a technical system, while the eye is part of a living organism that continually responds to changing conditions. The brain also interprets visual signals in ways that differ from the operation of a camera sensor.
A second approach is to ask students to design an investigation into one factor that affects image quality or visual experience. They might compare images taken under different lighting conditions, investigate how pupil size changes in response to light using a safe demonstration, or explore how colour appears under different light sources. Students should identify the variable they are changing, what they will observe, and what they need to keep consistent.
A third approach is to consider how improved ways of recording and interpreting light have changed science. Photography helps researchers document observations, while knowledge of vision contributes to medicine, neuroscience and the design of visual technologies. Students can choose one example and explain how understanding light has made it possible.
Use Science on This Day as a lesson starter
Science history can be a practical way to introduce a topic, particularly when the event leads directly to a question students can investigate. Rather than asking students to memorise a date, display a short account of Daguerre’s photographic process or Wald’s research and ask them to identify the scientific problem being addressed.
Students can then generate questions, discuss possible explanations and decide what evidence would help answer them. This works as a short starter, a reading activity or a transition into a larger unit on light, chemical reactions, the senses or scientific technology.
The November Science on This Day resource set provides 109 STEM stories across the 30 days of November. It includes an interactive HTML version with filters and classroom display features, editable slides with discussion questions, a filterable spreadsheet and a PDF version. Teachers can select an event to suit the topic they are teaching, whether they need a quick discussion prompt or a starting point for further investigation. You can also browse The Teaching Astrophysicist’s store for additional free and paid resources.
Looking ahead: more science history in November
The coming dates offer more opportunities to connect scientific ideas to real discoveries and technologies. November 19 provides a chance to explore the history of space exploration and the development of scientific instruments. Later in the month, stories involving computing, materials, physics, biology and astronomy can help students see how different disciplines contribute to our understanding of the world.
The key is to turn each event into a question. How does a chemical reaction record light? How does the retina detect it? What evidence would show that a new technology improves an investigation? These questions take students beyond the historical fact and towards scientific explanation.
November 18 is a reminder that light is both something we study and something that allows us to study almost everything else. From the chemistry of early photography to the biology of vision, the science of seeing offers a clear connection between the past and the questions students can investigate today.
Thanks for reading
Cheers and stay curious
Oliver - The Teaching Astrophysicist
