9 Brutal Truths About Images Formed by Thin Lenses.

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binoculars, lenses, vision @ Pixabay

Which of the following statements are true for images formed by thin lenses?

Today we will tell you about which of the following statements are true for images formed by thin lenses.

1. The image looks larger? 

2. The image flips or changes direction when looking at it from the edge of the lens? 

3. Images formed by thin lenses have a bright spot in their center? 

4. Images formed by thin lenses are upside down? 

5. Images formed by thin lenses are always blurry?

6. A person’s nose appears to be much wider than their forehead in images formed by thin lenses because they magnify vertical lines and compress horizontal ones, making a person’s nose look much farther away than it really is when using a straight-on view and making the forehead look closer than it really is when using an edge-on view.? 

7. The image formed by a thin lens will be upside down when seen from the side of the lens? 

8. Thin lenses always produce inverted images that are less than one-half life size? 

9. All of these statements true for images formed by thin lenses?

What are the advantages?

The above statements may be true for images formed by a thin lens whose focal length is approximately 40 millimeters (mm) or more. Since the upper limit of 60 mm exceeds 35 mm lens’s focal length, it should not be used. It is recommended to use lenses with less than 20 mm focal length, or to use totally free standing lenses. In general, “thin” and “thin lenses” refer to the characteristics of the images formed by these kinds of lenses: Thin meaning no more than 200mm in diameter (using a 2-meter height as an example.

What are the disadvantages?

The first two are self-evident, so we’ll focus on the third. Why does the center spot get brighter in images formed by a thin lens? Because the image is formed by a point source and not by a spherical one in this case. This means that the centers of focus of an image formed by a thin lens are much closer than they would be otherwise. By looking at some images, we can see that there is no change in their shapes when it is viewed from their center or edge (see the examples after these paragraphs). This is because that the lens does not provide any change in direction for light that hits it.

This is why thin lenses have no effect on the brightness of their images. An exception to this can be found, though, when using lenses with focal lengths shorter than 20 mm (see image above). These lenses are more like magnifying glasses than thin lenses . Figure 1 above shows the image formed by a thin lens and its brightness comparison before and after an object was placed in front of it. As can be seen, the image becomes brighter when objects are placed closer to it rather than farther away from it.

What are the features?

The fourth and fifth statements are not true for all images formed by thin lenses. The law of refraction states that light rays bend toward the normal (perpendicular to the surface) when they cross from one medium to another. This means that if an image is formed near the edge of a thin lens, it will appear pixelated because of its bending.

It should be noted that when we look at the backside of a thin lens we are viewing it through air and not through a thick material like those used in magnifying glasses; therefore, there will be no difference between viewing from the front or backside when using lenses whose focal lengths are less than 20 mm.

What makes it so unique?

One of the main features that mark thin lenses as a whole is their spherical quality. This means that the images formed by them are not distorted and have a natural appearance. The fifth feature is also not easily achieved with other types of lenses, since they are somewhat curved. Therefore, when using other lenses, only their image at their focal point will be in focus (see the third and fourth examples above). However, Thinlenses do not have this problem since their spherical surfaces make all parts of their images in focus at all times. Additionally, there is no change in brightness due to this characteristic because of its small size. This makes them ideal for close up photography or for portraits located far from the lens’s focal point.

Some more facts:

One of the most important features that make thin lenses so unique is their size and shape. Most thin lenses are made from acrylic glass (perspex) or from a material called PMMA (polymethyl methacrylate), which is a hard plastic used for accessories and decorations. Thin lenses are formed by cutting out spherically curved surfaces from these materials, and then gluing them together to form a single structure, as shown in Figure 1 above. As one can see, the result looks like a magnifying glass more than an ordinary lens due to its shape. 


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