One of the first works on curved mirrors can be attributed to the Greek mathematician Diocles who lived from 240-180 BC and who was the first scientist to demonstrate that a parabolic mirror can focus rays of light into a single point. He also noted that lenses with similar properties could be made in a similar way. The famous Croatian mathematician Marin Getaldić, who lived in Dubrovnik from 1568 to 1626, also dealt with mirrors. Getaldić dealt with geometry and parabolic mirrors so, even before Newton’s invention of the telescope, the people of Dubrovnik used a device to observe ships at a distance of 25-30 miles. In 1668, Isaac Newton built the first telescope that used a parabolic mirror. Curved mirrors are still used today when making telescopes.
This element consists of a concave and a convex mirror. A concave or converging mirror focuses incoming rays of light into a single point. A convex or diverging mirror scatters rays that enter parallel to the mirror. Concave and convex mirrors can show us how telescopes and similar devices work. In many stores, curved mirrors are used to make it easier to monitor shelves with goods. Such mirrors create an image we call a fisheye.
The shape of the mirror affects the image we see in it so the relationship of different parts of reflection can be altered with a curved mirror. Many mirrors are curved with the intention to highlight, reduce, or enlarge some parts of the image. On this element, you can explore how the shape of the mirror affects your reflection in it.
- Do these mirrors show your true “image”? Do you have mirrors like these at home? What do you think your mirror at home is like if it shows your true “image”?
- Write a word on a paper and look at the paper through the mirror. Is the image reversed? Does the same happen in a regular mirror?
- Can an image be reversed in one of the mirrors? If yes, in which one?
- Try to use a thread to highlight two rays that reflect from the mirror and enter your eye. Are the rays entering the mirror or leaving the mirror parallel?
- Why do you look smaller in one mirror and larger in another?
- Do you know any other curved mirrors that you use in your everyday life?
- If this mirror is spheric, can you determine its radius from the picture?
