Ray diagrams will also help us to study the nature, position and relative size of the image formed by the lenses. For drawing ray diagrams in lenses, we consider any two of the following rays. In case of a concave lens, the ray appears to diverge from the principal focus located on the same side of the lens, as shown in Figure b. This is shown in Figure a below. A ray of light appearing to meet at the principal focus of a concave lens, after refraction, will emerge parallel to the principal axis.
This is shown in Figure b below. This is illustrated in Figure a and b below. Image formed by a convex lens when the object is placed between the optical centre and the principal focus object between O and F 1 Characteristics of the image formed. The image is virtual.
The image is erect. The image is enlarged or magnified. The image is formed on the same side of the lens, behind the object. Applications When the object is placed between the optical centre of the convex lens and the principal focus, an erect and magnified image is formed. It is used as a magnifying glass or simple microscope in the following cases: 1.
It is used by the palmists to study the lines of the palm. It is used for seeing clearly the weave patterns of the cloth.
It is used as reading glass to read the fine print like letters. It is used to study biological specimens such as parts of the flower, etc. When the object is placed at the focus of a convex lens object at F 1 Characteristics of the image formed 1. The image is real. The image is inverted. The image is highly enlarged or magnified. The image is formed at infinity, on the other side of the lens. Applications The above case is used in making searchlights and spotlights in theatres.
In a searchlight, a powerful lamp is placed at the principal focus of a convex lens, which produces a powerful parallel beam of light. When the object is placed between F 1 and 2F 1. Characteristics of the image formed 1. The image is formed beyond 2F 2 , on the other side of the lens. Applications This type of image formation is used in film and slide projectors, when enlarged image of a small slide or film is formed on a screen.
When the object is at 2F 1 Characteristics of the image formed 1. The image is of the same size as the object. The image is formed at 2F 2 , on the other side of the lens. Applications This type of image formation is used in terrestrial telescope, for erecting the inverted image formed by the objective lens of the telescope.
Case V:. When the object is beyond 2F 1 Characteristics of the image formed 1. The image is diminished i. The image is formed between F 2 and 2F 2 , on the other side of the lens. Applications This type of image formation is used in a photographic camera, where a small, real and inverted image of an object is formed on the film.
When the object is at infinity such that the rays coming from it are parallel to the principal axis of the convex lens Characteristics of the image formed 1. The image is diminished to a point highly diminished.
The image is formed at F 2 , on the other side of the lens. Applications This type of image formation is used in a burning glass. When the rays of the sun are focussed by the lens of the burning glass on a piece of paper, the paper catches fire. The lens of the burning glass focuses the heat radiations on the paper as a result of which, the temperature of the paper rises to its ignition temperature and it catches fire.
Case VII: When the object is at infinity such that the rays coming from it are not parallel to the principal axis of the convex lens Characteristics of the image formed 1. The image is highly diminished. The image is formed on the focal plane on the other side of the lens. Applications This type of image formation is used for an objective lens in a telescope. It forms small, inverted image of far off objects in the focal plane in front of the eye lens. When the object is located at infinity such that the rays coming from it are parallel to the principal axis Characteristics of the image formed 1.
The image is highly diminished to a point size. The image is formed at F I ; on the same side of the lens as the object. When the object is located at infinity [such that the parallel rays from it are falling obliquely not parallel to the principal axis Characteristics of the image formed 1. The image is formed in the focal plane on the same side of the lens as the object. Applications This type of image formation is used in Galilean telescope, where concave lens acts as an eye lens.
When the object is anywhere between the optical centre O and infinity. The image is diminished. The image is formed between the optical centre O and the principal focus F 1 on the same side of the lens. I unit of Power is dioptre. Magnification Produced By Lenses The size of the image formed by a lens depends on the position of the object from the lens. For example, we have seen that if the object is placed beyond 2 F 1 , the image formed by a convex lens is diminished and if the object is placed between F 1 and the optical centre, an enlarged image is formed.
The linear magnification is the ratio of the height of the image to the height of the object i. It is so because for an inverted image v is negative in case of mirrors while it is positive in case of lenses. According to the New Cartesian Sign Convention: 1. Object should be taken on the left side to the lens. All distances are measured from the optical centre of the lenses.
The distances measured in the direction of the incident light are taken as positive whereas the distances measured against the direction of the incident light are taken as negative.
The distances measured upwards and perpendicular to the principal axis is taken as positive whereas the distances measured downwards and perpendicular to the principal axis is taken as negative. Does a light ray traveling from one medium? A ray of light will bend towards the normal when crossing the boundary from a medium in which it travels fast into a medium in which it travels slowly.
What causes dispersion of light? Dispersion occurs because the refraction of different colors is different. Light of different colours travel with same speed in vacuum. However they travel with different speeds in a refracting medium.
What does it mean to be denser? Use denser in a sentence. The definition of denser is something that is packed more tightly or is more crowded. An example of denser is an already packed subway car after another five people get on. What is medium in light? Air, glass, et cetera. What is the difference between reflection and refraction? What is the difference between light and reflection? Reflection is when light bounces off an object, while refraction is when light bends while passing through an object.
When you look at a mirror the light bounces of the mirror from different angles, so you can see your reflection. Which is denser medium glass of water? Glass is the denser than water because speed of light in glass is less than that of water. What is the meaning of medium in physics?
Scientific definitions for medium A substance that makes possible the transfer of energy from one location to another, especially through waves. SchoolTutoring Academy April 11, Comments. You might also like. Total Internal Reflection. Share : Email Facebook Twitter Linkedin. Enter your text here.
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