Optics Exploration:
Although this unit didn't have a project, our class did a lot of inquisitive research regarding the physics concept of light. In accordance, we also learned about the electromagnetic and color spectrum. We asked questions about the seemingly simple things that we take advantage of every day in life, things we've just accepted as true: for instance, why is the sky blue? We took a variety of notes, asked those questions, and did the research to answer them through using textbook and internet resources.
General Information:
Light is an energy that travels in electromagnetic waves within a certain range of frequencies. It's produced by vibrating electric charges in atoms. It only passes through materials whose atoms absorb the energy and immediately re-emit it as light (like glass). Light travels at 300,000 kilometers per second in a vacuum. Unlike sound, it doesn't require any medium to travel through. Light waves are transverse, so they can also be polarized. There is a whole electromagnetic spectrum of different kinds of light; however, the human eye can only see a small range of these.
Light can travel in many different forms of waves, and these are created by a change in frequency. The electromagnetic spectrum is extremely vast, and the light that we see in contrast is only a tiny, tiny part of the spectrum. There are:
1. Radio waves: around one million Hertz in frequency, cannot be seen by the human eye
2. Microwaves: around one billion Hertz in frequency, cannot be seen by the human eye
3. Infrared Waves: one trillion Hertz in frequency, and is the lowest frequency light that can be seen by the human eye; appears reddish
4. Light: with a slightly higher frequency than infrared waves, the light we can see is perhaps 2% of the electromagnetic spectrum
5. Ultraviolet Waves: higher frequency, the waves that are given off by the sun - can cause damage if exposed too much to UV rays
6. X-Rays: approaching one million trillion Hertz in frequency, dangerous to the human
7. Gamma Rays: one million trillion Hertz + in frequency, lethal to humans
What is light scattering?
A beam of light hits an atom, causing the electrons to excite. The smaller the atom, the higher frequency the light will be. (Also note that frequencies in light determine its color.)
Do tiny particles in the air scatter high or low frequencies? Larger particles?
Tinier particles scatter higher frequencies. Larger particles scatter low frequencies.
Why are clouds white?
In the atmosphere, light is scattered. Water droplets with different sizes, some of which are microscopic, make clouds. The range in sizes result in a variety of frequencies for scattered light. The larger droplets give off lower frequencies, while the smaller droplets give off higher frequencies. The overall result is a white cloud because such a wide range of colors are spread out.
Why is the sky blue?
The light scattered by nitrogen and oxygen (the primary components in our atmosphere) are relatively small particles. Because of this, the light and frequencies that occur split the colors blue and indigo, which are high-frequency colors. We see blue easier, since indigo is approaching ultraviolet which is out of the human view, so the sky is blue.
Why is the sky sometimes whitish, then?
The sky's color varies on particles and conditions. For example, if there is dust in the air, those larger particles split low-frequency colors. However, the oxygen and nitrogen continue to split high frequency colors. This mix of both colors creates white light, which is often referred to as ¨pure light¨ that contains all the colors mixed together. Hence the whitish sky.
Why are sunsets red?
Beams of light travel a longer distance through the atmosphere at sunset. More blue is scattered during this period, so by the time the beam gets to the ground, only the lower frequencies (red) survive.
Why is water greenish-blue?
Although it's kind of a counter-intuitive concept, physics tells us that the color we see in our eyes is the exact opposite of what the material is. For instance, a person wearing a black shirt, according to your eyes, is actually wearing a white shirt. The black you see is a result of the shirt reflecting all the colors, except for white, back at you. So in the ideal physics world, the shirt would actually be white. In this case, water molecules are at a size that absorb low frequency color: red. As a result, the opposite -- greenish-blue -- is reflected to our eyes, which is why we see water as that color.
Light is an energy that travels in electromagnetic waves within a certain range of frequencies. It's produced by vibrating electric charges in atoms. It only passes through materials whose atoms absorb the energy and immediately re-emit it as light (like glass). Light travels at 300,000 kilometers per second in a vacuum. Unlike sound, it doesn't require any medium to travel through. Light waves are transverse, so they can also be polarized. There is a whole electromagnetic spectrum of different kinds of light; however, the human eye can only see a small range of these.
Light can travel in many different forms of waves, and these are created by a change in frequency. The electromagnetic spectrum is extremely vast, and the light that we see in contrast is only a tiny, tiny part of the spectrum. There are:
1. Radio waves: around one million Hertz in frequency, cannot be seen by the human eye
2. Microwaves: around one billion Hertz in frequency, cannot be seen by the human eye
3. Infrared Waves: one trillion Hertz in frequency, and is the lowest frequency light that can be seen by the human eye; appears reddish
4. Light: with a slightly higher frequency than infrared waves, the light we can see is perhaps 2% of the electromagnetic spectrum
5. Ultraviolet Waves: higher frequency, the waves that are given off by the sun - can cause damage if exposed too much to UV rays
6. X-Rays: approaching one million trillion Hertz in frequency, dangerous to the human
7. Gamma Rays: one million trillion Hertz + in frequency, lethal to humans
What is light scattering?
A beam of light hits an atom, causing the electrons to excite. The smaller the atom, the higher frequency the light will be. (Also note that frequencies in light determine its color.)
Do tiny particles in the air scatter high or low frequencies? Larger particles?
Tinier particles scatter higher frequencies. Larger particles scatter low frequencies.
Why are clouds white?
In the atmosphere, light is scattered. Water droplets with different sizes, some of which are microscopic, make clouds. The range in sizes result in a variety of frequencies for scattered light. The larger droplets give off lower frequencies, while the smaller droplets give off higher frequencies. The overall result is a white cloud because such a wide range of colors are spread out.
Why is the sky blue?
The light scattered by nitrogen and oxygen (the primary components in our atmosphere) are relatively small particles. Because of this, the light and frequencies that occur split the colors blue and indigo, which are high-frequency colors. We see blue easier, since indigo is approaching ultraviolet which is out of the human view, so the sky is blue.
Why is the sky sometimes whitish, then?
The sky's color varies on particles and conditions. For example, if there is dust in the air, those larger particles split low-frequency colors. However, the oxygen and nitrogen continue to split high frequency colors. This mix of both colors creates white light, which is often referred to as ¨pure light¨ that contains all the colors mixed together. Hence the whitish sky.
Why are sunsets red?
Beams of light travel a longer distance through the atmosphere at sunset. More blue is scattered during this period, so by the time the beam gets to the ground, only the lower frequencies (red) survive.
Why is water greenish-blue?
Although it's kind of a counter-intuitive concept, physics tells us that the color we see in our eyes is the exact opposite of what the material is. For instance, a person wearing a black shirt, according to your eyes, is actually wearing a white shirt. The black you see is a result of the shirt reflecting all the colors, except for white, back at you. So in the ideal physics world, the shirt would actually be white. In this case, water molecules are at a size that absorb low frequency color: red. As a result, the opposite -- greenish-blue -- is reflected to our eyes, which is why we see water as that color.
Terms -
Refraction - wave reaches the boundary between two medias and changes direction as it passes through
[ This is why when you stick a pencil into a cup of water, the pencil looks like it's bending. It's actually just the light refracting! ]
Reflection - wave reaches the boundary between two medias and bounces straight back
Convex mirror - curves out, creating a smaller image
Concave mirror - curves in, creating a large, close-up image (like a compact)
Refraction - wave reaches the boundary between two medias and changes direction as it passes through
[ This is why when you stick a pencil into a cup of water, the pencil looks like it's bending. It's actually just the light refracting! ]
Reflection - wave reaches the boundary between two medias and bounces straight back
Convex mirror - curves out, creating a smaller image
Concave mirror - curves in, creating a large, close-up image (like a compact)
Optic Lenses: Lastly, in this unit, we learned about lenses. Terms associated with lenses are focal length, focal points, and images. One of the most common lenses is the converging lens, as shown below.
The focal length is simply the distance between the lens and the focal point, which is the point where the rays converge. There are many different kinds of lenses: some create a virtual image, and others create what's called a real image. Virtual images are situated between the focal point and the lens, whereas real images are past the focal point.
1. Microscope lens:
- creates a virtual image
- object is within the focal point
- takes small and close object, projects into a much bigger image
example: [ a projector ] takes a small image and then displays it as a much bigger image on a larger screen.
1. Microscope lens:
- creates a virtual image
- object is within the focal point
- takes small and close object, projects into a much bigger image
example: [ a projector ] takes a small image and then displays it as a much bigger image on a larger screen.
2. Human eye lens:
- the human eye takes in everything upside down, but then flips the image so a person sees everything right-side up
- microscopes appear upside-down because the images are already right-side up and the eye still flips it
- the human eye takes in everything upside down, but then flips the image so a person sees everything right-side up
- microscopes appear upside-down because the images are already right-side up and the eye still flips it
3. Divergent lens:
example: [fish-eye lens] takes a huge image and makes it really small `
example: [fish-eye lens] takes a huge image and makes it really small `
Reflection:
Personally, I really loved this unit on optics. I found out why the sky was blue. Before, I would have never wondered why. "The sky is blue," has just been something accepted by me ever since I was a kid. The unit really opened my eyes to the fact that even the simplest things in the world only happen due to physics, and science in general. Learning how to do lenses was a bit more difficult, and it took some trial and error in order to find what the exact foci and images were, but it was a great learning experience and I really enjoyed drawing those diagrams.
Personally, I really loved this unit on optics. I found out why the sky was blue. Before, I would have never wondered why. "The sky is blue," has just been something accepted by me ever since I was a kid. The unit really opened my eyes to the fact that even the simplest things in the world only happen due to physics, and science in general. Learning how to do lenses was a bit more difficult, and it took some trial and error in order to find what the exact foci and images were, but it was a great learning experience and I really enjoyed drawing those diagrams.