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By the end of the lesson, students will understand the structure of the human eye and how it functions.

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Students will be able to explain the phenomena of dispersion of light and how it creates a spectrum of colors.

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Students will learn about color blindness, its causes, and effects.

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Students will get an introduction to various optical instruments and their uses related to the human eye.

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Students will understand real-life applications of lenses in daily life and technologies.

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Teacher explains the anatomy and functioning of the human eye.

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Parts of the eye | Human eye & the colourful world | Khan Academy

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Students work in groups to create a model of the human eye using craft materials. Use Padlet to share their models and get feedback from classmates.

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Students will complete an online simulation to see how different colors are perceived by the human eye.

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Make a whole rainbow by mixing red, green, and blue light. Change the wavelength of a monochromatic beam or filter white light. View the light as a solid beam, or see the individual photons.

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Interactive activity where students use a color blindness test and discuss their findings.

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Color Blind Test info: This fairly common condition often goes undiagnosed, because you do not realize you aren't seeing colors as other people do. Yet testing for color blindness is simple - doesn't even require a trip to the doctor.

Simply look at the symbols below and enter the numbers that you can see. You'll get an instant result that will help you if you are struggling with color blindness, and which colors are more problematic.

Note: this is test is based off the standard Ishihara color plate test

This color vision test, known as the Ishihara Test, makes numbers out of dots that are a different color than the dots surrounding them. Someone who is color blind sees all of these dots as the same color, whereas someone with normal vision can distinguish the different colors. Ishihara Test a type of Color Blind Test is a fast and simple way to determine whether or not you are struggling.

Color Blind Test or the Ishihara test contains a number of colored plates, known as Ishihara plates. All of the plates contain a circle of dots appearing in random order of color and size. Most people will view the images differently (mostly Arabic numbers). Those with certain types of color blindness will see different numbers from those not affected by color blindness.

A color code happens when there is some information in the color of items being analyzed. These codes cannot be easily explained by those who have color blindness. This is the main reason why color should not be the sole criteria to provide information. The ideal way to avoid color-coding or color differences is to use Good graphic design to give information. This not only helps the color blind people but is also helpful to the normal vision people.
External info: Ishihara test Wikipedia

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Color Blind Test | Test Color Vision by Ishihara Test for Colorblindness

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Color Blind Test info: This fairly common condition often goes undiagnosed, because you do not realize you aren't seeing colors as other people do. Yet testing for color blindness is simple - doesn't even require a trip to the doctor. Simply look at the symbols below and enter the numbers that you can see.

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Explore the application of lenses in optical instruments using an online interactive tool.

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Optical instruments are the devices which process light wave to enhance an image for a more clear view. The use of optical instruments, such as a magnifying lens or any complicated device like a microscope or telescope, usually makes things bigger and helps us to see in a more detailed manner. The use of converging lenses makes things appear larger, and on the other hand, diverging lenses always get you smaller images.

While using a converging lens, it's important to remember that, if an object is at a larger distance than the image is diminished and will be very nearer to the focal point. While the object keeps on moving in the direction of the lens, the image moves beyond the focal point and enlarges. When the object is placed at 2F, which is two times the focal distance from the lens, the image and object become of the same size. When the object moves from 2F towards the focal point (F), its image keeps moving out of the lens and enlarges till it goes to infinity when the object reaches the focal point, F. As the object moves closer to the lens, the image moves in the direction of the lens from negative infinity and gets smaller when the object gets closer to lens.

Applications of Optical Instruments:

Multiple Lenses:

There are many devices like telescopes and microscopes, which use multiple lenses to create images. Analyzing any system having multiple lenses shows that it works in stages where each lens forms an image of the object. The original object will work as the object for the first lens and creates an image. This new image will be the object for the second lens and so on. You can see this with these examples.

Microscope:

A microscope has two converging lenses. This is because it is easier to get higher magnification with two lenses rather than just one. Use of one lens can magnify 5 times more and using a second will magnify 7 times, and you will get an overall magnification of 35 which is not possible in one lens. It's an easy procedure than to get magnification by a factor of 35 with a single lens. A ray diagram of the microscope arrangement is given below. Here you can see the image is the object for the second lens and the image formed by the second lens is the image that you would see when you looked through the microscope.

Telescopes:

As we use a telescope to view an object that is a very distant place, therefore, a telescope needs at least two lenses. The first lens forms a diminished image which is nearer to its focal point. This device is designed in a way so that real and inverted image formed by the first lens is just nearer to the second lens than its focal length. With the help of a magnifying glass, we get an enlarged image that is virtual. The final image then inverted with respect to the object. This doesn't really matter with the astronomical telescope. While observing an object which is on earth, we usually prefer a straight image that is obtained using the third lens.

Stay tuned with BYJU'S to learn more about optical instruments, lens, and much more.

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Optical Instruments - Definition & Examples | Types of Optical Instrument

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Optical instruments are the devices which process light wave to enhance an image for a more clear view. The use of optical instruments, such as a magnifying lens or any complicated device like a microscope or telescope, usually makes things bigger and helps us to see in a more detailed manner.

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Teacher observes group discussions and provides feedback.

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Students will take a short quiz on the structure of the eye and color theory.

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If you're seeing this message, it means we're having trouble loading external resources on our website.

If you're behind a web filter, please make sure that the domains *.kastatic.org and *.kasandbox.org are unblocked.

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The human eye and the colourful world: Quiz 1 | Khan Academy

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Learn for free about math, art, computer programming, economics, physics, chemistry, biology, medicine, finance, history, and more. Khan Academy is a nonprofit with the mission of providing a free, world-class education for anyone, anywhere.

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Students complete a worksheet on light dispersion.

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Dispersion of light interactive worksheet

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Liveworksheets transforms your traditional printable worksheets into self-correcting interactive exercises that the students can do online and send to the teacher.

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Students discuss what they learned about the human eye and how it perceives colors.

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Each student writes down one new thing they learned about the human eye and its functions.

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Students complete an additional worksheet on the functions of the human eye.

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The eye is an important and one of the most complex sense organ that we humans are endowed with. It helps us in visualizing objects and also helps us in light perception, color and depth perception. Besides, theses sense organs are pretty much similar to cameras and they help us see objects when light coming from outside enters into them. That being said, it is quite interesting to understand the structure and working of a human eye. It helps us also in understand how a camera also actually functions. Let's have a glance on human eye - it's structure and functioning.

Structure of Human Eye:

A human eye is roughly 2.3 cm in diameter and is almost a spherical ball filled with some fluid. It consists of the following parts:

Sclera: It is the outer covering, a protective tough white layer called the sclera (white part of the eye).

Cornea: The front transparent part of the sclera is called cornea. Light enters the eye through the cornea.

Iris: A dark muscular tissue and ring like structure behind the cornea are known as the iris. The color of iris actually indicates the color of the eye. The iris also helps regulate or adjust exposure by adjusting the iris.

Pupil: A small opening in the iris is known as a pupil. Its size is controlled by the help of iris. It controls the amount of light that enters the eye.

Lens: Behind the pupil, there is a transparent structure called a lens. By the action of ciliary muscles, it changes its shape to focus light on the retina. It becomes thinner to focus distant objects and becomes thicker to focus nearby objects.

Retina: It is a light sensitive layer that consists of numerous nerve cells. It converts images formed by the lens into electrical impulses. These electrical impulses are then transmitted to the brain through optic nerves.

Optic nerves: Optic nerves are of two types. These include cones and rods.

1. Cones: Cones are the nerve cells that are more sensitive to bright light. They help in detailed central and color vision.

2. Rods: Rods are the optic nerve cells that are more sensitive to dim lights. They help in peripheral vision.

At the junction of optic nerve and retina, there are no sensory nerve cells. So no vision is possible at that point and is known as a blind spot.

An eye also consists of six muscles. It includes, medial rectus, lateral rectus, superior rectus, inferior rectus, inferior oblique, and superior oblique. The basic function of these muscles are to provide different tensions and torques that further control the movement of the eye.

Functioning of the Human eye:

As we mentioned earlier that the eye of a human being is like a camera. Much like the electronic device, the human eye also focuses and let's in light to produce images. So basically, light rays that are deflected from or by distant objects land on the retina after they pass through various mediums like the cornea, crystalline lens, aqueous humor, the lens, and vitreous humor.

The concept here though is that as the light rays move through the various mediums, they experience refraction of light. Well, to put it in simple terms, refraction is nothing but the change in direction of the rays of light as they pass between different mediums. The table below shows the refractive indices of the various parts of the eye.

Having different refractive indexes is what bends the rays to form an image. The light rays finally are received and focused on the retina.The retina contains photoreceptor cells called rods and cones and these basically detect the intensity and the frequency of the light. Further, the image that is formed is processed by millions of these cells and they also relay the signal or nerve impulses to the brain via the optic nerve. The image formed is usually inverted but the brain corrects this phenomenon. This process is also similar to that of a convex lens.

In any case, now that that we have learnt something about the human eye, each eye is very important and they play a distinct part in helps humans to see.

Stay tuned with BYJU'S to learn more about human eye, the structure of human eye and more with the interactive videos.

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Structure of Human Eye | Parts of the Human Eye - Cornea, Sclera & Lens

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The eye is an important and one of the most complex sense organ that we humans are endowed with. It helps us in visualizing objects and also helps us in light perception, color and depth perception. Besides, theses sense organs are pretty much similar to cameras and they help us see objects when light coming from outside enters into them.

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Students start a small project on how animals perceive colors differently than humans.

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QBI researchers have advanced our understanding of how animals see and use colour, and how their colour vision has evolved.

Colour has an important role in reproduction and prey-predator interactions, although it serves diverse functions in various animals, said Professor Justin Marshall, co-author of a study undertaken with international colleagues.

"Colouration serves as an important source of information about animals, and the way in which colours are perceived differs between species," Professor Marshall said.

"I work with mantis shrimp, but also other oceanic animals because their colour vision is very different to ours. Mantis shrimp have four times as many colour receptors as we humans do. We have three - red, green, and blue - and they have 12."

Animals use UV light for specific purposes

The research (The biology of color), published in the journal Science, provides insight into how a variety of animals use colours invisible to the human eye, such as ultraviolet light, for species-specific purposes.

"Some animals use fluorescence or 'enhanced' colours," Professor Marshall said.

"We humans have reinvented this - and we use fluorescence in everyday objects, such as highlighter pens, or in washing power to achieve that 'whiter-than-white' look. Humans have realised that we can use chemicals to boost colours - light is taken in by the chemical and re-emitted, so it literally glows."

Understanding animal colour vision can help humans

Professor Marshall said an understanding of colours could be useful in everyday life.

"The challenge is to better understand how animals use their colour vision and their colours for survival," he said.

The new research follows earlier work co-authored by Professor Marshall in Philosophical Transactions of the Royal Society B (edited by Tim Caro, Mary Caswell Stoddard and Devi Stuart-Fox) following a workshop funded by Wissenschaftskolleg zu Berlin, which explored how the role of colours in animals' lives varied greatly across species, based on factors such as environment, physical factors (e.g. toxicity), and whether an animal is either predator or prey.

Two stomatopods (Odontodactylus scyllarus) wrestling. Colour forms a vital part of communication in these animals which have the most comprehensive set of colour receptors known in the animal kingdom.

Odontodactylus havanensis in cavity on the reef. Such stomatopod crustaceans possess the most advanced colour vision known in the animal kingdom with 12 receptors compared to our (humans) 3.

Detail of a blue-ringed octopus (Hapalochlaena sp.) being attached and eaten by a stomatopod crustacean (mantis shrimp). All octopus, including blue-rings are colour blind, while mantis shrimps possess four times as many colour channels than humans. The blue-ring colours are evolved to warn other species that can see the colour contrast of their rings. Stomatopods often ignore such warnings.

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Colour vision in animals: a comprehensive overview

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QBI researchers have advanced our understanding of how animals see and use colour, and how their colour vision has evolved.