Optical Phenomena optics

What is an Optical Phenomena?

An optical phenomena is the result of when light hits matter and creates something that our eyes can see. Some optical phenomenas are so commonly known that we may not even think about how they are formed. This ties into optics since these following examples are a result of light, reflection and dispersion.

Rainbows

Fun Fact: People used to believe that rainbows were magical bridges that gods used to travel to earth from heaven.

You may have noticed that whenever you see a rainbow form in the sky, it usually after it rains. This is because the raindrops that are floating around in the sky act as little prisms and breaks the white light into it's constituent (the colours of the rainbow) that we see once it reaches our eyes. Sorry to disappoint, but it's not magic, although the appearance still remains as beautiful. An example of the rainbow effect would be using a prism to shine white light onto. Sun light is made out of more colours than just white, those are shown when we view a rainbow. You will see that the light refracted once it hits the prism and shines the colours of the rainbow. Red, orange, yellow, green, blue, indigo and violet. It's in this order since each colour will correspond to a different wavelength. Red bends the least out of these colours, that why it's on the top and violet bend the most.

Refraction of white light creates a rainbow!
Top Left: Newfoundland, Top Right: Iceland, Bottom: Alaska

The Aurora Borealis, or the northern lights, is an optical phenomenon that occurs in the sky in the northern locations of the world. Examples would be Alaska, Norway, Yukon, Newfoundland and other parts of northern Canada and the world. This majestic view is adored by many and brings a lot people to the northern locations of the globes to see the sky change colour which doesn't happen everywhere. Economically, this can help create tourist attractions in places such as Whitehorse, Yukon and keep the cities managed with the money made. How does such a sight occur scientifically? Well, the centre of the earth has hot iron inside of it, this creates magnetic fields around the earth which are weakest in the north and the south of the globe. The charged electrons and ions from the sun come to these weak points through solar wind. Solar wind is the stream of particles that are charged from the sun that travel around the solar system. The electrons transfer energy to the nitrogen atoms that lie in the atmosphere and excites them. This connects to the energy and matter OLG since energy is being transferred and the northern lights are matter that can be seen by us ... which makes it an optical phenomena. The way these atoms "calm down" is by releasing energy in the form of photons which is the light which we see in the northern lights. The colour will depend on the nitrogen and oxygen and the altitude of the atmosphere. These colours can range from green-yellows, blues and even pinks and purples!

Mirages

A mirage is an optical phenomenon or illusion that make you think something is in front of you, but it's not. This can be natural occurring, and very common in hot places such as a dessert. An example of a mirage would be if a person sees a pool of water in the dessert that is not really there. This is not imagined or a result of drugs ... but there's a scientific explanation to explain these visuals!

A refraction phenomenon wherein an image of some distant object is made to appear displaced from its true position because of large vertical density variations near the surface; the image may appear distorted, inverted or wavering

- American Meteorological Society’s Glossary of Weather and Climate

What is refraction? Refraction is when the light wave passes through a different (slower) medium and bends. The amount of the bend differs on the material that the light hits. If you go to the ocean and see fish swimming below you, it appears to be in a different place than it is in reality. This is due to light refraction.

This is an example of a mirage on sea

Basically, this is caused by the bending of light. A mirage can happens when the earth's surface is hot and the light from a distant object is refracted ; this makes the object appear closer than it really is. This can also happen when the air above the ocean is warmer than the cool air above the water.

other mirages

Not all mirages have to be natural. You can even make your own mirage. The example used in class included a concave mirror used to make a mirage or hologram. The image of the object was shown above the mirror, reflected backwards, when the object was actually underneath.

Concave Lens Ray Diagram. The arrow is where the object actually is, the bold dot captioned "virtual image" is when the image appears to be. This is just one example of how a concave lens works.

Building on the last point, lenses produce dispersion and white light is refracted. If a picture is not taken correctly, you can see the refracted white light in the edges of pictures. This is called Chromatic Aberration when a camera fails to focus.

Chromatic Aberration
WHY IS THE SKY BLUE?

Something else related to optical phenomena is the sky. Have you ever wondered why the sky is blue - and not yellow, green or red? This is because of Rayleigh Scattering. By definition, this is "the scattering of light by particles in a medium, without change in wavelength". Out of all the light, blue light has a shorter wavelength and higher frequency which makes it more scattered. That is why the sky is blue. But doesn't violet have a shorter wavelength than blue? The reason the sky is not violet is since blue is a more intense colour in the sunlight, our eyes are more sensitive to blue and the atmosphere absorbs more violet which leaves us left with the pretty blue sky we know.

Honourable Mentions

Green Flash

Iridescence in bubbles

Sun halo in the sky

Social effects

These optical phenomenas are seen as beautiful, and many, seen as beautiful. Like I mentioned before, rainbows were once thought to be magic; something gods would travel to earth on or an arch with pots of gold at the ends. We see rainbows a lot in media such as movies, TV and in advertising. This designed us to view rainbows as happy and magical and a joy to look at. Examples of companies that used rainbows to advertise would be Lucky Charms and Skittles.

Economical

Like I mentioned before, people would want to see some these optical phenomenas such as the northern lights help keep these tourist places running. People from around the word, especially places not near the north or south pole, might want to travel to locations such as Northern Canada, Iceland, Greenland, Alaska etc. By tourist spending money in these place (which are usually not as popular in colder months compared to other parts of the world) and help their economy.

Pink Clouds

Environmental

Although I can't really relate any optical phenomenas to the environment, I can talk about atmospherical optics.

Pink Clouds

Personally, my favourite type of sky would be during a sunset or sunrise when the clouds and sky is pink and orange. But, have you ever though about why the clouds are pink when they are usually suppose to be white? Well, in areas with high pollution, such as cities, yellowish-pink clouds can occur due to nitrogen dioxide - but that doesn't always mean that they're formed because of pollution. Usually this happens for another simple reason, and that because of the scattering of sunlight around the earth! The scattering of the light in the atmosphere effects the colours of the sky during this time, and the details are up to the particles in the sky which control the directions of the light rays AND the wavelength.

reflection

If you want to see how optical phenomenas work with plane mirrors, you can find out for yourself.

SOURCE: http://www.physicscentral.com/experiment/physicsathome/rainbow.cfm

To quickly sum this experiment up, you have to fill a pan up with water and shine a white light into a mirror place in the water. You will see the bending of light and the white line creating a little rainbow of the colours it is made up of. SOURCE.

Bibliography

Understanding Physics, Shridha Chakravarti, Youtube, Retrieved from http://www.met.ie/education/pdfs_eng/Lesson%20Plan%20Optical%20Phenomena.pdf

Lesson Plan, Met éireann, Retrieved from http://www.met.ie/education/pdfs_eng/Lesson%20Plan%20Optical%20Phenomena.pdf

Rayleigh Scattering, The Editors of Encyclopædia Britannica, 1-11-1999, Retrieved from https://www.britannica.com/science/Rayleigh-scattering

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