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ABC Zoom - Refraction: why glass prisms bend and separate light

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overview of key point within the unit

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What is refraction of light - Optics for kids

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Fig. 7.Rainbows are formed by reflection and refraction of sunlight from falling water droplets.

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Khan Academy - advanced understanding

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Video transcript

before doing more examples with Snell's law which essentially amount to some math problems what I want to do is get an intuitive understanding for why this straw looks bent in this picture right over here to do that let me just draw a simplified version of that of that picture so let's draw this is the cup right over here we'll do a side profile of the cup so this is a side profile of this glass right over here it's the best that I can draw it and then let me draw the actual straw so I'm going to first draw the straw where it actually is so it's coming in off the side of the cup and the straw is actually not bending and goes to the bottom of the cup just like that and then it goes up like that and then it goes slightly above it and then it actually does Bend up here up here right over here and then the straw actually does Bend that is irrelevant to what we want to talk about what I want to do in this video is talk about why when we look over here when we look over here why does it look like the straw got bent and it all comes out of the refraction of the light as the light from the straw down here changes as it goes from one medium to another now we know from refraction indices or in just in general that light moves slower in water than a dozen air so it's slower slower in water and faster in air and faster in air so let's think about what's going to happen let's think about what's going to happen let me draw two points of let me draw two rays that are coming from this point on the straw right over here so if I draw one ray one ray right over here so I'm just going to pick an arbitrary direction so if I pick one ray just like that now when it goes from the slower medium to the faster medium what's going to happen to it and set a slight angle here so the left side of the ray is going to end up in the air before the right side and I'm just using this as a way of you know the I'm using the car example to kind of think about which way this light's going to bend so if you visualize it as a car or sometimes people visualize it as a marching band the left side of the marching band is going to get out before the right side is going to start moving faster so this is going to turn to the right so it's going to turn to the right now let me do another ray so let me down on the rate is coming from that same point let me I want it to go right along the straw so another ray just like that it will also turn to the right so it is also going to turn to the right now if someone's eye if someone's eye is right over here so that's your eye that's the eyelashes that someone's eye you can even draw their nose and all the rest if they're looking down where does it look like these two light rays let's say there I is big enough that it captured both of these Ray's where does it look like these two rays are coming from so if you trace both of these Ray's back if you just say assume that there was a line here that's what our eyes and our brains do if you assume that whatever direction this Ray is currently going it is the Ray that it's the direction it came from and same thing for this magenta ray and this magenta ray just like that it would look to this observer that this point on the straw is actually right over there and it would look and if you kept doing that for a bunch of points on the straw it would look like this point on the straw is actually right over here it would look like we could do it for this point on the straw it would look like that point on the straw is actually right over here so to this observer the straw would look like this it would look like it would look like something it would look it would look like it would look something like that it would look bent this part would look even though the light from here is going up and then up and then it moves out because it gets bent when you converge it back it would converge to this just like we saw with that first point the light from this point when it goes out and gets bent if you were to just extrapolate backwards from there new directions you get to that point so to this observer this point on the straw will look to be right over here even though the light was emitted down here and that's why the straw actually looks bent why it actually looks bent so this is all really just because of refraction from going from a slow or medium to a faster one so hopefully you find that a little bit interesting the next video will actually do some examples with Snell's law just to get ourselves comfortable with the mathematics

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Refraction in water (video) | Khan Academy

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Amazing Water Trick - Amazing Science Tricks Using Liquid

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Australian curriculum resource

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Our eyes have a small window at the front through which the light can enter. It is called the pupil. The pupil appears black because it is dark inside our eye. At the back of our eye is a sensitive sheet of nerves called the retina.

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TedEd Lesson series on How we see colour. Watch the video, think, dig deeper and discuss.

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Have you ever wondered what color is? In this first installment of a series on light, Colm Kelleher describes the physics behind colors -- why the colors we see are related to the period of motion and the frequency of waves. See his lesson on color here. By the way, here's a useful dictionary definition for frequency.

Color vision is the ability of an organism or machine to distinguish objects based on the wavelengths (or frequencies) of the light they reflect, emit, or transmit. Colors can be measured and quantified in various ways; indeed, a human's perception of colors is a subjective process whereby the brain responds to the stimuli that are produced when incoming light reacts with the several types of cone photoreceptors in the eye.

Visible light (commonly referred to simply as light) is electromagnetic radiation that is visible to the human eye and is responsible for the sense of sight. Visible light has a wavelength in the range of about 380 nanometres to about 740 nm - between the invisible infrared, with longer wavelengths, and the invisible ultraviolet, with shorter wavelengths.
Artist Neil Harbisson was born completely color blind, but, these days, a device attached to his head turns color into audible frequencies. Instead of seeing a world in grayscale, Harbisson can hear a symphony of color -- and even listen to faces and paintings. See his TED talk here.

Here's a Glossary of Color Science. Color is only one limiting factor of human perception. Once you understand how humans perceive color, research ways that we percieve other things using our eyes.

Colors are of philosophical interest for a number of reasons. One of the most important reasons is that color raises serious metaphysical issues, concerning the nature both of physical reality and of the mind.

Have you ever wondered what it's like to be color blind? Could an increased ability in one of our senses be caused by our lack of ability in another? "No Such Thing As Color" is a nine-minute documentary that shows us what the world looks like through the eyes of Evans Forde, a color blind musician with insightful opinions about the importance of color in our lives.

People love eating pizza, but every style of pie has a different consistency. If "New York-style"--thin, flat, and large--is your texture of choice, then you've probably eaten a slice that was as messy as it was delicious. Colm Kelleher outlines the scientific and mathematical properties that make folding a slice the long way the best alternative...to wearing a bib. See Colm's Lesson on physics here.

The trichromatic theory that is presented in this lesson does not account for all aspects of color perception. For example-if you stare at a red square, then shift your focus to a white background, why do you see a green afterimage? Try this for yourself . And if you shine a blue light on a yellow banana, the banana will still seem yellow, even though it should appear green. A similar effect can be seen using abstract shapes.

Effects such as these are partially explained by the opponent-process theory and the retinex theory. These theories indicate that the eye and brain carry out some processing that is more complicated than simply detecting the wavelengths of light. The opponent-process theory suggests that there are cells that activate as red under certain conditions, and green under other conditions (the same goes for blue and yellow). The retinex theory suggests that our visual system compares surfaces to their surroundings to help determine what we perceive as color. Like the trichromatic theory, neither of these theories fully accounts for color perception by itself, and the full truth may be a combination or of all three, as well as new theories yet to be formulated.

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There are three types of color receptors in your eye: red, green and blue. But how do we see the amazing kaleidoscope of other colors that make up our world? Colm Kelleher explains how humans can see everything from auburn to aquamarine.

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BBC Science resource on distant sight

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Everything you need to know about how telescopes work.

Human eyes can see long distances. In fact the Andromeda Galaxy can be seen with the naked eye and that's 2.5 million light-years away. But even a massive galaxy, like Andromeda, appears to us as a tiny point in the sky.

It makes sense that as an object gets further away it becomes harder to see. But why this happens helps us understand how vital telescopes have been in exploring the universe.

As an object gets further away less of its light will reach your eye. The image takes up less space on your retina (the light-sensitive tissue at the back of your eye), making the image smaller. This makes details of the image harder to see.
Take a tour of the human eye and see how it works
To make a distant object appear brighter and larger, we effectively need a bigger eye to collect more light. With more light we can create a brighter image, we can then magnify the image so that it takes up more space on our retina.

The big lens in the telescope (objective lens) collects much more light than your eye can from a distant object and focuses the light to a point (the focal point) inside the telescope.

A smaller lens (eyepiece lens) takes the bright light from the focal point and magnifies it so that it uses more of your retina.

A telescope's ability to collect light depends on the size of the objective lens, which is used to gather and focus light from a narrow region of sky.

The eye piece magnifies the light collected by the objective lens, like a magnifying glass magnifies words on a page. But the performance of a telescope depends almost entirely on the size of the objective lens, sometimes called the aperture.

If you've ever seen light bend through a prism you probably have an idea of where the problem lies with a refracting telescope; it's the lens.

When light travels through glass it slows down, that's why it bends. Lenses are shaped perfectly to bend light in particular ways. But the amount light bends depends on the wavelength, or colour, of the light.

White light is a mixture of all colours, from red to violet. Red light bends the least and violet light bends the most.

When white light travels through the objective lens, the different colours bend at different angles and are focused at slightly different points. Different coloured images are misaligned creating a blurry image with fringes of colour along the boundaries that separate dark and bright parts.

Reflecting telescopes magnify distant objects using the same principle: more light is collected and focused to a point and this is magnified so that it fills your field of vision.

But instead of using a lens, a curved mirror (primary mirror) collects the light and reflects it to a focus. Because light doesn't pass through the mirror, it doesn't bend the different colours by different amounts, the way a refracting lens does.

A small mirror (secondary mirror) is placed in the path of light from the primary mirror to reflect the image towards the eyepiece. The secondary mirror must be very small so that it doesn't block the light from the distant object as it travels to the primary mirror.

Another benefit of using mirrors instead of lenses is that big mirrors are easier and cheaper to make than big lenses. Reflecting telescopes can be much larger and therefore look deeper into space.

Jodrell Bank Observatory

Jodrell Bank Observatory was established in 1945 by Sir Bernard Lovell

Since then it's played an important role in researching meteors, quasars, pulsars, masers and gravitational lenses

Jodrell Bank's Lovell Telescope was used to track Sputnik 1, the first probe to go into space

Radio waves aren't just for listening to your favourite songs, they occur naturally all over the universe. In fact, they are a special type of light that humans can't see. They can be found emanating from clouds of gas where stars are born, as well as the centres of galaxies.

Many strong sources of radio waves are invisible in normal light, so looking at radio waves reveals a completely different picture of our universe. Even objects like the Sun and planets can reveal new features when viewed with radio telescopes, like Jodrell Bank.

Radio waves are also better at travelling long distances than shorter wavelengths, so we can get clearer signals from very distant objects in radio than we can in normal light.

The large dish acts like the primary mirror in a reflecting telescope, but it needs to be much larger to reflect the long wavelength radio waves. These are reflected up to a smaller mirror which reflects the images back to a receiver. The information from the receiver is then processed by computers to create colour images which we can see.

The problem with telescopes on Earth is that light being received has to pass through our atmosphere. Although a clear sky may seem transparent, light can be scattered by the molecules in our air. This is what makes stars twinkle!

The atmosphere also blocks certain kinds of light, including X-rays, ultraviolet and infrared light. This effect is beneficial for life on Earth, but to see these kinds of light from stars and galaxies, we need to venture outside of our atmosphere.

That's why the Hubble telescope can take such incredible images of distant galaxies, allowing us to explore the history of our universe.
Watch Brian Cox uses Hubble to see galaxies 13 billion years old

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How do telescopes let us see so far into space?

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Everything you need to know about how telescopes work. Human eyes can see long distances. In fact the Andromeda Galaxy can be seen with the naked eye and that's 2.5 million light-years away. But even a massive galaxy, like Andromeda, appears to us as a tiny point in the sky.

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How it works website

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The structure of the human eye is so complex that it's hard to believe that it's not the product of intelligent design, but by looking at the eyes of other animals, scientists have shown that it evolved very gradually from a simple light-dark sensor over the course of around 100 million years. It functions in a very similar way to a camera, with an opening through which the light enters, a lens for focusing and a light-sensitive membrane at the back.

The amount of light that enters the eye is controlled by the circular and radial muscles in the iris, which contract and relax to alter the size of the pupil. The light first passes through a tough protective sheet called the cornea, and then moves into the lens. This adjustable structure bends the light, focusing it down to a point on the retina, at the back of the eye.

The retina is covered in millions of light-sensitive receptors known as rods and cones. Each receptor contains pigment molecules, which change shape when they are hit by light, triggering an electrical message that travels to the brain via the optic nerve.

How we see

The back of the eye is covered in a layer of light-sensitive cells measuring just fractions of a millimetre in thickness. When photons of light hit the pigments inside the cells, it triggers a cascade of signals, which pass through a series of different connections before they are transmitted to the brain.

First, they move through interneurones and then to neurones known as ganglion cells. These cells are cross-linked, able to compare adjacent signals, filtering out some of the information before passing it on to the brain. This helps to improve contrast and definition. The neurones travel across the back surface toward the optic nerve, which relays the information into the brain.

As the two optic nerves enter the brain, they cross over, coming together at a point known as the optic chiasm. Here, signals from the left side of both eyes are diverted to the left side of the brain, and vice versa, allowing the images from both eyes to be combined and compared.

The signals enter the brain via the thalamus, which separates the incoming information into two parts, one containing colour and detail, and the other movement and contrast. The messages then move to the back of the brain, and into the visual cortex. The cortex is laid out so that it mirrors the back of the retina, allowing a detailed image to be reconstructed.

Colour vision

Open your eyes, and you are met with an array of different colours, but amazingly you can only detect three different wavelengths of light, corresponding to green, blue, and red. Combining these three signals in the brain creates millions of different shades.

Each eye has between 6 and 7 million cone cells, containing one of three colour-sensitive proteins known as opsins. When photons of light hit the opsins, they change shape, triggering a cascade that produces electrical signals, which in turn transmit the messages to the brain. Well over half of our cone cells respond to red light, around a third to green light, and just two per cent to blue light, giving us vision focused around the yellow-green region of the spectrum.

The vast majority of the cone cells in the human eye are located in the centre of the retina, on a spot known as the fovea, measuring just fractions of a millimetre across. Light is focused on this point, providing a crisp, full-colour image at the centre of our vision. The remainder of the retina is dominated by 120 million rod cells, which detect light, but not colour.

We are so used to seeing the world in red, green and blue that it might seem strange to think that most other animals cannot, but three-coloured vision like our own is relatively unusual. Some species of fish, reptiles and birds have four-colour vision, able to see red, green, blue and ultraviolet or infrared light, but during mammalian evolution, two of the four cone types were lost, leaving most modern mammals with dichromatic vision - seeing in shades of just yellow and blue.

This was not a problem for many early mammals, because they were largely nocturnal, and lived underground, where there was little need for good colour vision. However, when primates started moving into the trees, a gene duplication gave some species the ability to see red, providing a significant evolutionary advantage in picking out ripe red fruit against the green leaves.

Even today, not all primates can see in three colours; some have dichromatic vision, and many nocturnal monkeys only see in black and white. It is all down to environment; if you don't need to see all of the colours in order to survive, then why waste energy making the pigments?

Seeing in three dimensions

Our eyes are only able to produce two-dimensional images, but with some clever processing, the brain is able to build these flat pictures into a three-dimensional view. Our eyes are positioned about five centimetres (two inches) apart, so each sees the world from a slightly different angle. The brain compares the two pictures, using the differences to create the illusion of depth.

Discover more amazing science in the latest issue of How It Works magazine. It's available from all good retailers, or you can order it online from the ImagineShop. If you have a tablet or smartphone, you can also download the digital version onto your iOS or Android device. To make sure you never miss an issue of How It Works magazine, make sure you subscribe today!

Plus take a look at:
Top 5 facts about vision What is the maximum distance the human eye can see if unobstructed? How do sunglasses protect your eyes?

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Science of vision: How do our eyes enable us to see? | How It Works Magazine

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The structure of the human eye is so complex that it's hard to believe that it's not the product of intelligent design, but by looking at the eyes of other animals, scientists have shown that it evolved very gradually from a simple light-dark sensor over the course of around 100 million years.

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Short video introducing the eye

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website covering the basic questions about the eye. Don't click on the video, it is for younger children.

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The human eye is the organ of sight.

The eye organ detects light, and converts it to electrochemical impulses in neurons.
Rod and cone cells in the retina allow us see light, figure out perception of depth (how near and far objects are) and to differentiate color.

What are the types of eye?

Not all eyes are the same. Humans have a different eye type from insects (compound eyes). Some eyes are complex and some are simple, like the eyes in larva. There are over 10 different eye types. The human eye can distinguish between 10 million colors and is very similar to a camera because they both have lenses.

What is an eye made up of?

The human eye is not a full sphere, rather it is a fused two-piece unit. A transparent window at the front of the eye is called the . This lens-like structure focuses the light reaching it. The hole in the center of the iris is called the and the coloured part of the eye is the . The is very important as it is the inner lining of the eyeball. Receptor cells called and make up the retina. Black and white vision is seen by the rods and color vision is received by the cones. These messages are then sent to the brain via the optic nerve, which runs from the eye to the brain.

How do eyes work?

The individual components of the eye work in a manner similar to a camera. Each part plays a vital role in providing clear vision. A human eye is like a camera with the cornea, which is like a lens cover. As the eye's main focusing element, the cornea takes widely diverging rays of light and bends them through the pupil, the dark, round opening in the center of the colored iris. The iris and pupil act like the aperture of a camera.

Next in line is the lens which acts like the lens in a camera, helping to focus light to the back of the eye.

The very back of the eye is lined with a layer called the retina which is similar to the film in a camera. The retina is a membrane containing photoreceptor nerve cells that line the inside back wall of the eye. The receptor cells (rods and cones) of the retina change the light rays into electrical impulses and send them through the optic nerve to the brain where an image is perceived. The center 10% of the retina is called the macula. This is responsible for your sharp vision, your reading vision.

The peripheral retina is responsible for the peripheral vision. As with the camera, if the "film" is bad in the eye (i.e. the retina), no matter how good the rest of the eye is you will not get a good picture.

The human eye is remarkable. It accommodates to changing lighting conditions and focuses light rays originating from various distances from the eye. When all of the components of the eye function properly, light is converted to impulses and conveyed to the brain where an image is perceived.

Why are some eyes brown and other eyes blue?

Eye color is determined by the amount and type of pigments in the eye's iris. Humans and other animals have many variations in eye color, such as blue, brown, gray, green and others. Blue color is determined by multiple genes. It was once believed that a blue eye color is a simple recessive trait but this has been shown to be wrong. The genetics of eye color are very complicated. Almost any parent-child combination of eye colors can occur.

Why do we blink?

Blinking our eyes keeps them clean and moist. Blinking helps to wash tears over our eyeballs. Also, if something is about to hit our eye, we will blink automatically (for protection).

Interesting Facts

A human eye weights 28 grams.

Nearsighted people cannot focus on object in the distance.

Farsighted people cannot focus on near objects.

The human eye can distinguish 500 shades of gray.

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The human eye is the organ of sight. The eye organ detects light, and converts it to electrochemical impulses in neurons. Rod and cone cells in the retina allow us see light, figure out perception of depth (how near and far objects are) and to differentiate color. Not all eyes are the same.

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If you have a UK VPN at home you'll be able to watch the videos but if not you'll still be able to read and explore these links to find out more about light.

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BBC Bitesize - KS2 Science - Light and dark

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KS2 Science Light and dark learning resources for adults, children, parents and teachers.

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Exploratorium - illusions

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How much do we really know about how we see the world? Find out as our expanded SEEING collection makes its debut.

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12 illusions to test your brain

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Exploratorium - bird in a cage

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Do you have a staring problem? See what happens when you stare at something long enough, then look at a blank background. Experiment with the relationship between your brain and the cone cells on the back of your eye and see what happens when some of them get fatigued.

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Bill Nye the science guy - the eyeball
If the video doesn't load you can press download (downward arrow) or go to the website to watch it on https://www.youtube.com/watch?v=HkcxRYdhQ5s

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10 minute video covering the parts and functions of the eye

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Human Eye _ #aumsum #kids #education #science #learn

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Bill Nye short clip the eye

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Brain pop.com login if required
Username Ecolintnp
password np

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Just look at how pupils, lenses, and irises enable us to see the beauty in the world--including that piece of chocolate cake!

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This video is funny but a bit annoying. If you can keep watching there is a lot of good information about the eye ...

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Exploratorium - cow's eye dissection / exploration

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Learn how to dissect a cow's eye in your classroom. This resource includes: a step-by-step, hints and tips, a cow eye primer, and a glossary of terms.

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MAKING CONNECTIONS
Why are light and colour important to sight?
Group Activities:
Draw a partner's eye and label the diagram with all the information you can.
Scavenger hunt outside for materials with different properties
Independent learning:
Eyewitness sight video - Listening & note taking on the parts & functions of the eye in different species
Reflection:
Discussion - do all species have the same sensory ability? What factors affect our sight? What is the structure of the human eye and what function do these parts have? Can you add more to your eye diagram now? What is special about the way we see? Which scientist showed that light could be split into the colours of a spectrum?

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Copy of Copy of unit 1 a - activity 1 treasure hunt eye terminology.docx

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click the download button if it doesn't play (downward arrow) as it is a big file it takes time to load. Or click on the you tube link here https://www.youtube.com/watch?v=k8XRt6RTNfc

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Eyewitness test with answers - 23 Sep 2018 - 17-31

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FAIR TESTING
Introducing and exploring the idea of 'fair testing'.
Group Activities:
Races in the playground
The tennis ball drop
Independent learning:
Using a set format to write up the results of the tests.
Reflection:
Discussion / lessons learned
What would you do differently & why?

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Hello, and welcome to PADLET. Pallet is an online notice board, so you can 'pin' all sorts of useful information and ideas on it. I use it as a way to share really interesting information with you.

This padlet is packed with information linked to our Science Dual Language Unit 1 - about sight, light and colour.

You can move left and right and up and down to explore all the columns of information I have pinned here for you.

If a video doesn't load you can press download (downward arrow), go to the website to watch it on the link provided or ask your teacher to renew the link.

If you have been absent or need to reference documents used in class you can also find it here under the weekly  column.

If you feel like a challenge and want to extend your learning try the Challenge column.

Now go explore and grow your brain !