Can you see right now? Good for you. Your lenses are working. Also there’s probably light involved. Unless you are a god. In which case, also good for you? I guess?
Light is needed to see. That is a basic statement. You know what else is a basic statement? Light travels in waves. However, it takes a lot of work to prove that. I worked with Anika and Grace to prove that light travels in waves. We used a comparison of waves in water and light waves traveling against mirrors to shine onto a different surface. They travelled in the exact same way. This was the first part of our light unit.
The next part of our unit was mirrors! We did experiments to test how light reacted when shone at a plane mirror, a convex mirror, and a concave mirror. A convex mirror is shaped like a backwards c, and a concave mirror is shaped like a regular c. To set up the experiment, Anika and I used a ray box, a baffle, a piece of paper, and a protractor. A ray box is a box with a light bulb inside. You plug it in to create a light ray. A baffle is a thin square with a different number of slits on each side that you slide in front of the light ray to create a different number of light rays.

We discovered that for the plane mirror, the light would reflect at the exact same angle of the incident ray. However, for the convex and concave mirrors, it changed. When light was shined at the convex mirror, the reflected light rays diverged, which means they spread further apart. When light was shined at the concave mirror, the reflected light rays converged, which means they all touched each other.

The next light experiment was shining light through liquid. We shined the light through vegetable oil, ethanol, and water.

We discovered that inside the liquids, the light bounced at a different angle from the incident ray, which is the ray that is originally shined from the ray box. The angle of how the light bounced is called the angle of refraction. However, after the light had travelled through the liquid, it travelled at the same angle as the incident ray, instead of the refracted ray. That means that the incident ray was on both sides of the liquid, and the refracted ray was inside the liquid.

The next part of the unit was lenses, which we learned about in our Big Fat Lenses Lab (BFLL). In the BFLL, we learned about three types of lenses- biconcave, biconvex, and plane, like the mirror. When light was shined at them, the refracted rays on the other side did the exact same thing the reflected rays of the mirrors did. The refracted rays of the biconcave lens converged, like the concave mirror, and the refracted rays from the biconvex lens diverged, like the convex mirror. The rays shone through the plane lens, or Lexan block, remained straight at the same angle.

To figure out why the rays converged, diverged, or stayed the same, we learned about focal points. It’s easiest to draw the path of the light to figure out where it will go.

There are three basic light rays that bounce off an object into a lens or mirror- one is parallel to the normal, one goes through the focal point, and one goes through the center. In a convex or concave mirror, the center is where the center would be if the mirrors stretched all the way into a sphere. In a biconcave or biconvex lens, it is just the center of the lens. The focal point is the point where anything between it and the mirror or lens would project a virtual image, and anything on the others side would create a real image. A virtual image is when the light rays reflected by the object never actually meet, and a real image is when the light rays do meet.

Once those three basic light rays have been reflected or refracted, they each do a specific thing. The reflected or refracted ray did certain things based on what it was shined through originally. The ray that had been shined through the focal point reflected or refracted parallel to the normal, the ray that had been shined parallel to the normal reflected or refracted through the focal point, and the ray that had been shined through the center reflected or refracted through the center again. However, for the lenses, there were two focal points. For the biconcave lens, the ray that began parallel to the normal reflected along the focal point on the side of the lens that the object was on, and the ray that began going through the focal point went through the focal point on the opposite side of the lens. The biconvex lens did the opposite.

We also watched this documentary about light, and how animals use light. It was really informative, and it showed how amazing bioluminescence is. I would highly recommend it.

I think that this documentary gives clear examples of how light rays bounce, and I think it’s so cool how the camera obscura works. Over the summer, I got to see one firsthand, when the eclipse happened.

At the time, I really had no idea how that worked, but now I know how the light rays had to bounce to create that image.

Another thing about that documentary that was really interesting to me was the thorough description of the Islamic world did for optics. It shows that they were the first to figure out how the eye saw things, and the first to figure out that light reflected off of objects to meet our eyes. It was a Muslim man who created and used a camera obscura to figure out how light moves- in a straight line, unless it’s reflected by something.

Another of the driving questions for this unit was ‘Why are humans drawn to light?’

I think the answer to that question is fairly complicated. One of the first inventions was the invention of fire, way back when we had just learned to walk upright. Even now, we watch tons of different kinds of magnificent light shows for entertainment. Fireworks are our way of celebration. I think we’re so interested in light because sight is really our dominant sense, and light controls what we see. Light affects us every second of every day, and it makes sense that we would want to control it.

I feel like after learning about light, I can really understand how the world works better.

Thanks for reading my blog post!