Rainbows are one of the most famous and beautiful phenomena in our Hawaiian Islands, and anybody who grew up here has seen the brilliant bands of light over the Ko'olaus or above Diamond Head. But what is a rainbow? Simply put, we've learned that a rainbow is a product of light refraction, as the white light from the sun behind the viewer passes through the raindrops and is diverted to the viewers eyes. The reason the rainbow makes a "bow" shape is because the Earth blocks a good deal of the sun's light, resulting in the semicircular arc form the light that does pass the Earth.

Visual aids helped me to understand this concept more fully. The following section is taken from the University of Carolina's website:

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The traditional diagram to illustrate this is shown here as adapted from Humphreys, Physics of the Air. It represents the path of one light ray incident on a water droplet from the direction SA. As the light beam enters the surface of the drop at A, it is bent (refracted) a little and strikes the inside wall of the drop at B, where it is reflected back to C. As it emerges from the drop it is refracted (bent) again into the direction CE. The angle D represents a measure of the deviation of the emergent ray from its original direction. Descartes calculated this deviation for a ray of red light to be about 180 - 42 or 138 degrees.

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It was this understanding of the physical aspects of rainbows that helped me to explain the following picture, taken from Kailua Beach near sunset:

It looks like a little patch of rainbow floating out over Flat Island. I though of two possible explanations for this phenomenon, and in reality it could be both. The first is that there are only water droplets in the air (rain) at that one spot. The second is that the setting sun is being blocked by some landscape feature, most likely the Ko'olau mountain range, and only that relatively small section of sky is receiving direct sunlight. In both cases, the sun is setting behind the camera, which meshes with the UCar diagram above. This is a cool picture made evn cooler by an understanding of physics!!1! :D

Blue Angels

A while ago the Blue Angels were in the islands, and I had the opportunity to go watch them perform their tight formation flying. As I watched in awe as the jets screamed overhead, I realized that they were creating sonic booms! This is because the jets were flying faster than the speed of sound (which varies according to temperature but is usually around 343 m/s), creating the amplified sound waves we call sonic booms. IT WAS AWESOME!!

I also got to thinking about the medium affecting the velocity of sound. Since sound actually travels relatively slowly through air when compared to other mediums, creating a sonic boom in another medium (underwater, for example) would require far greater speed. In addition, an underwater sonic boom would probably result in physical waves as well, and a large enough one could theoretically cause a tidal wave or similar large disturbance. Perhaps sound could be used for underwater demolition without causing harm to the local ecosystem! THE POSSIBILITIES ARE ENDLESS! SCIENCE RULEZ!!!1!!

Physics Blog 8: Torque

Recently I went to one of my brother's kayaking races and was struck by the physics concepts that I witnessed!!

A kayaker

I noticed that kayakers spread their hands out when gripping the paddle. At first I wondered why they didn't just keep both hands together in the middle, as that would accomplish the same motion. However, I quickly figured out that this was a matter of TORQUE!! By spreading the grip apart, the kayaker increases the lever arm (r), which in turn increases the torque he can apply (T) given the equation T=Fr where F is the force. I am beginning to understand just how much physics applies to sports - understanding the physics behind certain actions can give more of an edge than raw strength. PHYSICS RULEZ!!!