Age 7-9 Research cards years Euclid About Euclid was a Greek mathematician. He was fascinated by shape and created a new type of mathematics called geometry that described shapes and angles. He was born in 325BC and moved to Alexandria in Egypt in 322BC where he lived and studied until his death in 270BC. Light rays are straight lines.
Working scientifically We only see things that light rays fall upon. If light rays do not fall on an Euclid carefully observed shape in the object, then we can’t see it. world around him and noticed he could use mathematical descriptions You see an object in a particular of shape and angles to describe light direction because light rays come from rays and their behaviour. that direction.
Euclid used his observations of light in If light rays come into the eye from a the world around him to make some large range of angles, then the object predictions about light rays: will seem big. If they come into the eye from more or less the same angle, the object will appear small. When an object is closer, then light rays come in from a larger range of angles than if it is were further away.
Euclid used drawings and diagrams to record and communicate his ideas. He A Latin also used mathematics to describe light translation rays. Euclid wrote a book called Optiks of Euclid's about the geometry of light and seeing. book, Optiks
image: Vatican Library Age 7-9 Research cards years Ibn Sahl About Ibn Sahl was born in 940AD and was a Persian mathematician and physicist who lived in Baghdad. Sahl wrote a number of books and letters between 970AD and 990AD that described his physics experiments and ideas. Ibn He carefully observed the paths of Sahl died in 1000AD. rays of light as they reflected off different mirrors. He recorded his observations in diagrams to illustrate what he had seen in his experiments. Working scientifically Ibn Sahl was interested in how mirrors When he began to observe light rays and lenses could be used to focus travelling through glass lenses, he light rays so that they could be used observed that the rays bent in the to burn things. He carefully read and same way as they did when they studied books by the reflected from a curved mirror. Sahl Roman astronomer measured angles of light Ptolemy to find out all he rays and used mathematics could about how light to describe the patterns he bends when it goes image: Milli Library observed in his through different experiments. He also used transparent materials. models to try to explain how light travelled through Sahl carried out different materials, experiments with curved imagining the beams of mirrors to find out how light were cone shaped. different curved, reflective surfaces could For years to come, other focus light to a point. He thought this Persian scientists wrote about Sahl’s was a useful property of light because experiments and his scientific laws if a flammable material was placed at about the behaviour of light. the focus point it would catch fire. Age 7-9 Research cards years Roger Bacon
About Roger Bacon was a medieval philosopher and Franciscan monk. He was born in England in 1219 and is famous for being one of the first people to use scientific experiments to build new knowledge about the world. Roger Bacon died in Oxford in 1292.
Working scientifically Bacon was interested in eyesight and He noticed how light rays would how the eye worked. To learn more, he sometimes bend when they travelled read books by Ptolemy and Ibn Sahl into glass and he did experiments to that had been translated into Latin. The learn more about lenses. Bacon books caused him to ask further enjoyed observing the night sky and questions about how we see, and these used his knowledge of lenses to help questions led him to carry out him make more careful observations of investigations to find out more. the Moon, planets and stars. He also suggested how lenses might be used to Roger Bacon built models of the eye to make ‘spectacles’ to improve people’s help him understand how it worked. He eyesight. also dissected animal eyeballs to learn more about the parts of the eye. Bacon Noticing that rainbows were caused by carried out many different experiments sunlight, Bacon carried out experiments to help him understand how we can see to model how rainbows formed to help things. explain why they happened. He was always impressing people with his demonstrations, once making a camera obscura (pinhole camera) so that people could safely observe solar eclipses. Age 7-9 Research cards years Willebrord Snellius
About Willebrord Snellius was a Dutch astronomer and mathematician. He was born in Leiden in the Netherlands in 1580. He is remembered for his work using mathematics to describe how light travels through transparent materials and Snell’s Law is still used by physicists all over the world today. Snellius died in 1626 at the age of 46. In his experiments, Snellius took measurements of the angle that light rays hit a glass block and then the angle that the rays were bent to in Working scientifically the glass. He looked carefully at the Snellius was interested in how light data he collected and spotted a travelled through glass. He was an pattern. He then described this astronomer and liked to make pattern as a mathematical equation. instruments with lenses to help him make careful observations of the night He tested his equation on different sky. transparent materials and discovered that the relationship was always So that he could true. He could use his equation to make better predict exactly how much a light ray instruments for would bend without actually doing his astronomy, an experiment. Snellius planned and carried out Snellius’ work was not published experiments to until the next century, but Snell’s Law find out how is still used by secondary school glass lenses students today. Snell's Law also helps affected light engineers designing fibre optic rays. cables used for fast internet communications. Age 7-9 Research cards years Isaac Newton
About image: The Granger Collection, New York Isaac Newton was one of the most influential scientists of all time. He was born in the village of Woolsthorpe in England in 1643. He really enjoyed school and became a very talented mathematician and physicist. As an adult he spent many years working at Cambridge University. Isaac Newton died in 1727.
Working scientifically Newton wondered if all the different colours of light behaved in the same In 1666, Isaac Newton observed that way as white light. He experimented when a ray of white light entered a with mirrors and lenses and discovered triangular glass block, called a prism, that they did. Using his new it left the prism as a spectrum of understanding of coloured light, colours. The spectrum always included Newton tried to explain how we see red, orange, yellow, green, blue, coloured objects. He said that the indigo and violet light. He came to colour that we see an object as, is the the conclusion that the prism bent colour (or mixture of colours) of light light rays of different colours by that the object reflects. different angles. Being a keen astronomer, Newton had Newton also showed that the observed that lenses in telescopes often multicoloured spectrum of light made created a spectrum of light that made by a prism could be turned back into it difficult to make careful observations white light again by using another of planets and moons. To solve the prism. He came to the conclusion that problem he designed a new, improved white light was a mixture of all the telescope which used mirrors instead of colours of the spectrum. lenses – a reflector telescope. Age 7-9 Research cards years Christiaan Huygens
About Christiaan Huygens was a Dutch physicist, mathematician, astronomer and inventor. He was born in the Netherlands in 1629. Huygens is famous for his work on forces and light as well as his discovery of Saturn’s moon, Titan. He died in 1695. In his experiments, Huygens made measurements of light rays travelling through calcite crystals. He looked Working scientifically carefully at his data to find patterns Huygens was very curious about light and explain what was happening. This and read many books to learn more was when he came up with the idea including work by Snellius and Newton. that light travelled like waves. Huygens had observed that some materials, such as calcite crystals, bent Huygens’ wave model of light could light in two directions and his also be used to explain why light observations could not be explained by reflected from a mirror and the the current theories about light. He bending of light when it travelled from decided that he needed to come up one transparent material to another. with a new model to describe the behaviour of light so that he could Huygens met Isaac Newton in London explain this new phenomenon. in 1689, they had very different ideas about light and disagreed with each other’s theories, but they respected and were inspired by each other’s work.
In 1801, a famous physicist called Thomas Young carried out some more experiments with light that agreed with Huygens’ theory that light was a Looking through a calcite crystal wave. Age 7-9 Writing framework years
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