• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

Formation of Lens

Free essay example:

Case Study:

Every lens has a focal point, where all the light directed at that lens converges or diverges and the distance between the lens and that point is called the focal length.

The eye normally focuses on the image on the retina. This is because the convex lens inside the eye can become wider or narrower to compress the light. Sometimes, however, something inside the eye is not functioning correctly. This makes the visualization blurry or mixed up. I am going to identify these disorders and how lenses correct them.

Defects of Eye

These are the different types of eye defects that may be corrected by lenses:

Myopia also known as nearsightedness is one of the defects of the eye. A person who is suffering from this disease only see objects that is near to the eye clearly. This means you cannot see objects at a distance which appeared to be blurred. If the eye has myopia the eye is too long and the image falls short of the retina when the target object is far away.

The image shows that in myopia the image fall short of the retina when the target object is far away.



A concave lens is a diverging lens which works similar to the convex mirror. This lens is thicker towards the edges and thin in the middle and is used in helping correction of nearsightedness. All images produced by concave lenses are virtual, erect and reduced.


Hypermetropia also known as hyperopia or farsightedness is another type of eye defects. Hyperopia is the opposite of myopia means that a person who is suffering from this disease able to see objects far from the eye visibly. In this case the eye is shorter than normal and the image focuses behind the retina this means it doesn’t focus even when it reaches retina. The images focus at the back of the retina.



A convex lens is a converging lens which works much like a concave mirror. This kind of lens is thicker in the middle and thinner towards the edges, like the lens in a magnifying glass. The image is changed by the position of the object in relation to the focal length and the radius of curvature. This lens helps people who are suffering from farsightedness.


The power of a lens with focal length f is P=1/f where lens power is measured in dioptres, D. The distances between the image and the source are related to each other by the lens equation:

1/V = 1/U + 1/F

Where U = object distance

            V = image distance

        F = focal length

In this equation the term f is a permanent number, called the focal length of the lens. It tells everything about the lens itself, including the material it is made from and the curvature of the surfaces.

Checking people’s health is very important. Each defects of eye has different needs of lens with different focal length or point. Ensuring that people can see as well as possible is a very useful contribution to their health. By correcting the lens of an eye people will able to see clearly vision.


It is not always possible to balance red and purple vision, as red light has different wavelength, different wave speed in different mediums and different refractive index than the green light.


  1. Salters Horners Advanced Physics (ISBN: 978-1-40589-6023)
  2. Information about defects of eye  Virtualsciencefair.org/2005/dong5a0/public_html (February 12 2009)
  3. librarythingquest.org/C006027/html_ver/mis_def.html (February 6 2009)
  4. Notes from class.

This student written piece of work is one of many that can be found in our AS and A Level Microscopes & Lenses section.

Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

Related AS and A Level Science Skills and Knowledge Essays

See our best essays

Related AS and A Level Microscopes & Lenses essays

  1. To investigate the relationship between the distance between a lens and an object, and ...

    Although I did check this, the experiment I conducted was not very accurate and subject to the same problems that my main one was. Grease, dust of small pieces of dirt on the lens could also affect the results, by changing the refraction if the light, much the same as if the lens were of poor quality.

  2. To investigate the relationship between u and v for a convex lens.

    This is shown by my third graph. This shows a way of finding v or u. The only way you can balance this equation is for u to be 0 so therefore where the line crosses the y axis that is where v is. 1/v=1/f-1/u. There were no anomalous results in my experiment.

  1. Measuring the focal length of a lens for red and green light- Case Study

    The way a converging lens works is that it moves the rays closer together bringing the focal point near the retina. This helps to fix hypermetropia. Limitation of lenses: As you can see using lenses has many benefits when correcting certain eye defects, these are that the strength of the

  2. My experiments focus is to obtain an accurate measurement for a specific lenss power.

    This means less external light (i.e. from classroom ceiling lights) will reach the lens and interfere with the image being formed. Less interference leads to a clearer image and so hopefully I will be able to obtain more accurate 1/V values.

  1. Proving the lens formula.

    marker, then measure the Image distance, using the front of the screen as the marker. Use the 30cm rule so that the mm can be measured as accurately as possible. * The lens can move around 5 mm and still produce a clear and focussed image on the screen.

  2. Relationship Between U and V For a Convex Lens

    to produce a curved line for u over v, producing a reciprocal graph.' As you can see from that the graph I have is produced a reciprocal graph, as predicted. Due to the fact the graph produced is a reciprocal graph; it means that there is a tighter distribution of

  1. Investigating the Positioning of Real Images formed by a Convex Lens.

    Increasing the aperture lets more light into the camera, but it can also lead to some focusing problems. High quality cameras have expensive multi-element lenses which produce sharply focused images even at wide apertures. When I used the camera I wondered how it worked and how the rays were formed on the screen, so I took the camera apart.

  2. Use of the material Zerodur in the KECK observatory telescope. The very low CTE ...

    Stainless steel - 17.3.5 Clearly then, with varying conditions within the building in which the telescope is housed; using other materials such as stainless steel would have caused major problems for the mirror. For example, using stainless steel; CTE: 17.3 �m m-1 K-1 Expansion for a temperature change of 5

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work