As I researched many possible innovations that have been invented to solve a problem facing the people of the world I came across a very old yet still widely used invention in the world today, the lens.
The lens was first developed around 750 BC by the ancient Egyptians and Mesopotamians (an area in west Asia). Today lenses are used in a multitude of different areas throughout engineering and undoubtedly many other areas of practice, helping people across the world to have a better quality of life. The importance of the lens is in my opinion hugely understated and only as a direct result of my study of the lens through this project have I come to understand their importance to the world we live in.
When people think of lenses naturally the first thing that comes to mind is the lenses in reading glasses and of course this is the most common use of the lens in today’s world and may be the greatest innovation that the lens has been used for. The thought of a world where people are not able to read books or enjoy scenery and the beauty of nature, watch a sporting event or do simple tasks such as knitting or sewing would be an actual problem that people would face if it were not for the creation and innovation of the lens. Of course, the lens has had many more uses throughout time from their use in lighthouses to guide ships to shore in the dark of night to their involvement in unearthing and furthering our understanding of the world and universe around us through their use in both microscopes and telescopes.
The world without the lens
There is no one particular problem that the lens was created to solve directly, but its innovation helped to improve and impact greatly on a myriad of different difficulties and problems across many different aspects of life along with solving problems that were facing people in centuries gone by. As I mentioned earlier the most renowned use of the lens belongs to its fundamental function in spectacles and eye wear. According to many sources including Wikipedia, the first recorded use of lenses as a magnifier for reading/assistance in helping to improve vision was through Roger Bacons invention of the magnifying glass in 1250. It then followed that the first pair of glasses were produced in Pisa Italy twenty-six years later in the year 1286. The problem of diminishing sight as one gets older is a problem that humanity has been facing for centuries and will face for many more to come. This age-old problem stems from the lens in the human eye which is controlled by the ciliary muscle.
Over our lifetimes this muscle deteriorates and does not change the angle of the lens in the eye as significantly as it once did. This means that light is not bent as much when entering the eye and is not focused directly on the retina at the back of the eye resulting in a blurry or unclear image. This is where the lens in a pair of glasses come into play and take up the role of bending the light either less or more (depending on whether the person is long or short sighted) to focus it properly on the retina in the eye and create a clear image. Of course, this is a problem in itself in that people’s condition may vary depending on whether they are long or short sighted and therefore the light entering ones eye may need to be bent differently in different circumstances. This is where the different types of lenses come into fruition. There are two main types of lenses used in spectacles, the first being a convex or converging lens and the other being a concave or diverging lens. The difference between the two is quite simple, the convex lens bends or refracts the light entering your eye to focus distant images better by focusing them on the retina while the concave lens is used to curve light outward to make the image look bigger like that in reading glasses. This is a basic diagram of the difference in shape between a convex and concave lens. As can be seen the convex lens is much thicker in the middle and becomes narrower as it moves outwards while the opposite is true for the concave lens.
How do lenses work?
The above diagrams illustrate the basic principle of how both convex and concave lenses work. These lenses work on the principle of refraction where light enters the glass and is bent as it travels at a different speed in the glass than it does in the air thus bending or refracting. Of course, this means that the glass present within the lens must be of a very high quality. It may not seem like it to the naked eye but the ordinary basic glass that is used in everyday items such as windows is not suitable for lens making due to the imperfections and impurities within the glass. Much of this glass has air bubbles and various other defects that if used in lenses would distort the light entering the lens and create a blurry image. These are more commonly known as aberrations among experts.
Problems that the lens helped to solve: Of course, like many other innovations throughout history the lens does not have a sole purpose of being used in spectacles and glasses. Lenses have allowed us an otherwise inaccessible glimpse into both the smallest and largest aspects of the world around us through the use of microscopes and telescopes. Most people have used either a telescope or microscope during some stage of their life be it for work or just as a pastime. Yet these instruments have been responsible for more discoveries and unveiling more amazing information about the world around us than many people can comprehend. Some of the most significant and useful problems that the lens was responsible for solving are as follows:
- Diminishing eye sight
- Guiding boats and ships to dock through their use in lighthouses
- Allowing scientists, physicists and engineers to investigate both the vastness of space and the minuteness of compounds and elements that make up the matter around us
- Used in car headlamps to spread the light over a wider field of view and allow the driver to see further in the darkness.
Guiding ships to dock: Throughout history the ship has been a fundamental part of life for humanity bringing people across the world, carrying valuable cargo from place to place and of course used in the discovery of new lands. This was part of everyday life throughout the ages, yet it brought with it many challenges. one of them being bringing the ship in to shore in the darkness of night. There are records of the first lighthouses consisting of a fire being lit on a raised platform so that sailors could see where the shore line was from far off and prepare to dock. This was the most basic form of indication that the shore was near at this time, but this did not offer the sailors a reliable and safe indication as it could only be seen closer in to shore. This meant that boats and ships often got caught in reefs and shallow shorelines meaning goods could not be delivered but more worryingly people often died as the ships sank. The introduction of the lens in lighthouses was therefore a significant improvement in offering sailors a reliable and more importantly, an extremely visible indicator of shore lines. Lighthouses began to use the Fresnel lens in the 1800’s. This was a much-improved lens upon the original lens used in lighthouses created by Thomas Rogers as it was much smaller lighter thinner and focused the light much better as it did not absorb as much of the light as the previously used lens. This meant that light could be protruded out to sea much further and would also be much more intense. This image shows an example of a Fresnel lens that would have been used in a lighthouse to focus and intensify the light being protruded out to sea in comparison with a basic concave lens like that used by Thomas Rogers at the beginning of lens technology in lighthouses.
Headlights in vehicles: When people think of lenses very few people consider the head lamps in a car as an example, yet lenses play a very important part in allowing the driver of a vehicle to see further along the road than would be possible without a lens. In the very first motorcars lights consisted of kerosene lamps that had to be lit manually by the driver to see in front of them during the night time even though electric bulbs had already been invented at that time. This of course was not practical and was soon replaced. The problem with this system was that it was used so that pedestrians and other motor vehicle drivers could see the driver of the vehicle from further off and avoid an accident however, it did not act as a medium to allow the driver to see very well in front of them which resulted in accidents and damage being done to the vehicle due to poor road conditions. This was then replaced by the first electric headlamps in 1898 but these were of low quality and did not offer very good visibility. The inclusion of a concave lens therefore changed how people travelled at night time as it allowed drivers a much wider and better field of view, reducing accidents and allowing more vehicles to drive safely at night time.
Telescopes: As the stars and planets that scientists’ study are so far away the light coming from these bodies is very faint and not very visible to the human eye. According to “BBC – GCSE Bitesize science” the light rays coming from these bodies are almost parallel and so two convex lenses are used in a telescope to magnify the light entering your eye. These lenses used are of different powers and refract the light so that the user can see a much clearer and distinct image. This has been the basis for many major scientific discoveries for example the first viewing of craters on the moon.