How Do Lens Refract Light
How does a Lens Refract Light?
Different Lenses refract light in different ways. First, we will look at a double convex lens. Several light rays will approach the convex lens in a parallel manner. After they approach the lens, each ray will refract towards the normal. The light is passing from an optical less dense medium (Air) into a more dense medium (such as plastic or glass) at this boundary. Since the light rays are passing the boundary from a less dense medium in which light travels fast (optically less dense) into a more dense medium in which light travels slowly (more optically dense), light will refract towards the normal line. This is demonstrated by the two incident rays in the diagram above about the refraction by a converging lens. Once light refracts from the boundary and …show more content…
enters the lens, it will travel in a straight line until it reaches the boundary at the back of the lens. With this boundary, the rays will refract away from the normal since light is travelling from a dense medium into a less dense medium. The two rays converge at a point, this is known as a focal point.
When rays travel from the focal point to the lens, the rays will refract as they enter the lens and refract again as they leave the lens. As light enters into a more dense medium, they bend towards the normal; and as they exit the lens into a less dense medium, they bend away from the normal, The rays will then travel parallel.
Now we will observe the refraction within a double concave lens. Let’s assume that several rays are approaching the lens in parallel manner. Upon reaching the lens/boundary, light will refract towards the normal because it is travelling from a less dense medium into a more dense medium. This is demonstrated on the diagram on the right. Once the light bends from the boundary and into the lens, it will travel in a straight line until it exits the boundary at the back of the lens. With this boundary, light will refract away from the normal since it is travelling from a more dense medium into a less dense medium. These conditions also applies to the convex lens.
Because a concave lens is shaped differently than that of a convex lens, the light rays will not converge at a certain point during refraction.
The incident rays will, rather, diverge upon refraction within the lens. Because of this, double concave lenses cannot reveal real images, but images that are virtual (not real). But if we backtrack the refracted rays, the rays will then intercept at a point; this is the focal point. The concave lens will have a negative focal length since the rays that travelling parallel as it enters the front of the lens to the principal axis, will diverge as it exits the lens.
Now let’s assume that the light rays are travelling towards the focal point of the lens. Light rays will approach the focal point from the opposing side of the concave lens, this is due to the negative focal length of the lens. As we already know, the light rays will refract as they enter the lens and refract again as they exit the lens. Because the light is entering a more dense medium, refraction occurs towards the normal and as they approach the less dense medium, refraction occurs away from the normal. These rays will then travel parallel to the principal axis.
Refraction
Rules:
Now that we have learnt about Refraction for both Concave and Convex lens, lets recount on the conditions that need to be met in order for refraction to occur for both lens:
Converging Lens:
Incident Rays travelling parallel to the principal axis, will bend/refract within the lens and converge at a certain point located on the opposite side of the lens (Focal point)
Incide Rays travelling FROM the focal point to the lens, will bend/refract within the lens and travel parallel to the principal axis as it exits the lens.
Incident Rays that travel through the middle/center of the lens will continue in the same direction.
Diverging Lens:
Incident Ray travelling parallel to the principal axis will ben/refract within the lens and travel in a direction that its extension/backtrack will pass through the focal point.
Incident Ray travelling towards the focal point as it approaches the lens will bend/refract within the lens and travel parallel to the principal axis.
Incident Ray that passed through the middle/center of the lens, will continue in the same direction equivalent to how it entered the lens.
Image Formation of Lens:
The Convex/Converging Lens produces real and virtual image compared to concave/diverging lenses which produces only virtual images. The formation of images for lenses are the same as the image formation for both plane and curved mirrors. The images are located anywhere the observer (our eyes) is looking, as long as we view the image of the object within the lens. So, if we backtrack/trace the light rays, we will find that they intersect at a certain point upon refraction through the lens. For us to view the image of the object, we must sight along these the direction of this point. If we had more than one observer, each of them will sight the image along different lines of sight because either way, they would see the image as each line of sight converges where the image is located. This is demonstrated in the diagram on the right. This tells us that the image is real since the light rays are literally passing through the location of the image.
If we were to find the focal point (f), distance of the object from the lens (do), or the distance of the formed image from the lens (di) for both Convex and Concave. We can use the formulae:
Different Lenses refract light in different ways. First, we will look at a double convex lens. Several light rays will approach the convex lens in a parallel manner. After they approach the lens, each ray will refract towards the normal. The light is passing from an optical less dense medium (Air) into a more dense medium (such as plastic or glass) at this boundary. Since the light rays are passing the boundary from a less dense medium in which light travels fast (optically less dense) into a more dense medium in which light travels slowly (more optically dense), light will refract towards the normal line. This is demonstrated by the two incident rays in the diagram above about the refraction by a converging lens. Once light refracts from the boundary and …show more content…
enters the lens, it will travel in a straight line until it reaches the boundary at the back of the lens. With this boundary, the rays will refract away from the normal since light is travelling from a dense medium into a less dense medium. The two rays converge at a point, this is known as a focal point.
When rays travel from the focal point to the lens, the rays will refract as they enter the lens and refract again as they leave the lens. As light enters into a more dense medium, they bend towards the normal; and as they exit the lens into a less dense medium, they bend away from the normal, The rays will then travel parallel.
Now we will observe the refraction within a double concave lens. Let’s assume that several rays are approaching the lens in parallel manner. Upon reaching the lens/boundary, light will refract towards the normal because it is travelling from a less dense medium into a more dense medium. This is demonstrated on the diagram on the right. Once the light bends from the boundary and into the lens, it will travel in a straight line until it exits the boundary at the back of the lens. With this boundary, light will refract away from the normal since it is travelling from a more dense medium into a less dense medium. These conditions also applies to the convex lens.
Because a concave lens is shaped differently than that of a convex lens, the light rays will not converge at a certain point during refraction.
The incident rays will, rather, diverge upon refraction within the lens. Because of this, double concave lenses cannot reveal real images, but images that are virtual (not real). But if we backtrack the refracted rays, the rays will then intercept at a point; this is the focal point. The concave lens will have a negative focal length since the rays that travelling parallel as it enters the front of the lens to the principal axis, will diverge as it exits the lens.
Now let’s assume that the light rays are travelling towards the focal point of the lens. Light rays will approach the focal point from the opposing side of the concave lens, this is due to the negative focal length of the lens. As we already know, the light rays will refract as they enter the lens and refract again as they exit the lens. Because the light is entering a more dense medium, refraction occurs towards the normal and as they approach the less dense medium, refraction occurs away from the normal. These rays will then travel parallel to the principal axis.
Refraction
Rules:
Now that we have learnt about Refraction for both Concave and Convex lens, lets recount on the conditions that need to be met in order for refraction to occur for both lens:
Converging Lens:
Incident Rays travelling parallel to the principal axis, will bend/refract within the lens and converge at a certain point located on the opposite side of the lens (Focal point)
Incide Rays travelling FROM the focal point to the lens, will bend/refract within the lens and travel parallel to the principal axis as it exits the lens.
Incident Rays that travel through the middle/center of the lens will continue in the same direction.
Diverging Lens:
Incident Ray travelling parallel to the principal axis will ben/refract within the lens and travel in a direction that its extension/backtrack will pass through the focal point.
Incident Ray travelling towards the focal point as it approaches the lens will bend/refract within the lens and travel parallel to the principal axis.
Incident Ray that passed through the middle/center of the lens, will continue in the same direction equivalent to how it entered the lens.
Image Formation of Lens:
The Convex/Converging Lens produces real and virtual image compared to concave/diverging lenses which produces only virtual images. The formation of images for lenses are the same as the image formation for both plane and curved mirrors. The images are located anywhere the observer (our eyes) is looking, as long as we view the image of the object within the lens. So, if we backtrack/trace the light rays, we will find that they intersect at a certain point upon refraction through the lens. For us to view the image of the object, we must sight along these the direction of this point. If we had more than one observer, each of them will sight the image along different lines of sight because either way, they would see the image as each line of sight converges where the image is located. This is demonstrated in the diagram on the right. This tells us that the image is real since the light rays are literally passing through the location of the image.
If we were to find the focal point (f), distance of the object from the lens (do), or the distance of the formed image from the lens (di) for both Convex and Concave. We can use the formulae: