How do atmospheric events happen?
Have you ever wondered why the sky is blue, how a mirage or a rainbow is generated, why we see the sky on the road (as in the image) or what are the beautiful southern lights of Antarctica? These are all natural atmospheric phenomena produced by light or, more correctly, electromagnetic waves. By answering this essential question, you will learn about light and its properties as well as how various atmospheric events occur!!
Introduction to LIGHT
Episode 4 of The Forces of Nature: The Pale Blue Dot. In this final episode Professor Brian Cox explores the science behind how light colours our planet. He travels to Iceland, where the delicate splendour of a moonbow reveals the colours that paint our world, and he visits a volcano to explain why the sun shines. By exploring how sunlight transforms the plains of the Serengeti, drives the annual migration of humpback whales to the Caribbean and paints the moon red during a lunar eclipse, Brian reveals the colour signature of our life-supporting planet. Finally, at an observatory high in the Swiss Alps, he shows how these colours aren't simply beautiful, but that understanding how they're created is allowing us to search for other Earths far out in the cosmos. |
3.7) The Electromagnetic Spectrum
Visible light is actually made of an electric field and a magnetic field moving together and hence visible light is actually an electromagnetic wave.
Visible light is actually made of an electric field and a magnetic field moving together and hence visible light is actually an electromagnetic wave.
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There are many different other types of electromagnetic waves - a) Gamma rays b) x-rays c) Ultraviolet radiation d) visible light e) infrared radiation f) Microwaves g) Radio and TV waves Our lives would be very different if we could not use these electromagnetic waves. They are very important to us and the many different technologies that we rely on. |
3.8) Properties of Electromagnetic Waves
All Electromagnetic waves have the following properties 1) They are transverse waves 2) They travel at 300,000 km per second - in other words they are the fastest things in the Universe 3) They transmit energy without transporting matter 4) They can travel through a vacuum hence they are the only things that can travel through space 5) They can be ABSORBED, TRANSMITTED, REFLECTED OR REFRACTED Also white visible light actually consists of all the colours of the rainbow ie ROYGBIV. So we are going to always picture white light as shown opposite. |
A) Absorption and Transmission
A substance is transparent when all or most of the light passes through and we can see objects on the other side clearly
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A substance is Translucent when the surface of the material is rough and light passes through but is scattered. Hence we cannot see objects on the other side clearly
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A substance is opaque when no light travels through them and is instead reflected or absorbed
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Question: Explain what happens, using a diagram, in each of the three situations provided below.
a) White light hits a transparent piece of red glass
b) White light hits a translucent piece of red glass
c) White light hits an opaque piece of red glass or red cardboard
a) White light hits a transparent piece of red glass
b) White light hits a translucent piece of red glass
c) White light hits an opaque piece of red glass or red cardboard
Check Your Understanding
Two lights are arranged above a white sheet of paper. When the lights are turned on they illuminate the entire sheet of paper (as seen in the diagram below). Each light bulb emits a primary color of light - red (R), green (G), and blue (B). Depending on which primary color of light is used, the paper will appear a different color. Express your understanding of color addition by determining the color that the sheet of paper will appear in the diagrams opposite. |
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Task 2) Why is the sky blue and the sun yellow?
Use diagrams to explain why our beautiful sky appears blue and the sun appears yellow when the sun is emitting white light. |
1) The dress is definitely blue and black. Scientists used a colour analysis program to determine the actual colour of the dress.
2) Your eyes are easily fooled. Our eye-brain combination is actually NOT that good at judging the colour of something HOWEVER it is very good at comparing. In this picture there is no skin anywhere for our brains to compare the colour to and the background is washed out so we have a difficulty determinign the colour of the dress. Look at the two images of the chess pieces. The chess pieces are EXACTLY the same colour in both images. Take a GOOD look! 3) Ambient (or the surroundng) lighting also affects the colour of an object. Our brains are constantly using the information around you to determine how to compensate for this. This is called COLOUR CONSTANCY. For example; If you hold a piece of white paper in front of you in a room that has only red lighting, you will still see the paper as white even though it is reflecting only red light back to your eye. Now as the background is very bright, your brain may think that the dress is in shadow. If you assume that the front of the dress is in shadow (thanks to the bright blurry background light), your brain will apply colour constancy and remove the blueish hue of the shadow — and bingo, the dress is white. 4) The top part of the dress is reflecting back light and this could make your brain think that the dress is actually illuminated - not in shadow at all and you will see the dress as blue. AS with all optical illusions, we have been blinded by the light!! |
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C) Refraction
Refraction is the bending or the slowing down of waves when they pass through different mediums. We are going to look at two sorts of waves - water waves and light waves. Refraction happens all around us, everyday.
Refraction is the bending or the slowing down of waves when they pass through different mediums. We are going to look at two sorts of waves - water waves and light waves. Refraction happens all around us, everyday.
i) Waves coming parallel to a boundary from low density to higher density medium
When this happens, light will slow down and the light waves bunch closely together. An example of this is light going from air into water. A bird's eye view of this is provided by the diagram opposite. An example that shows light slowing down and hence distorting the image you see is shown opposite. People's legs in water look really short. |
Extension Activities
1) Refraction Experiment
Complete the refraction experiment using the ray box kit
Complete the refraction experiment using the ray box kit
2) Learn about Snell's Law
Interesting Resources
1) What gives the MORPHO butterfly its magnificent blue?
What does it mean to be blue? The wings of a Morpho butterfly are some of the most brilliant structures in nature, and yet they contain no blue pigment -- they harness the physics of light at the nanoscale. |
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