Phase Change

Why does a phase change graph have flat lines?

A phase change graph demonstrates how the temperature is affected by how much energy is added to a substance. For example, in order for an ice cube to melt it has to absorb energy from it's surroundings. As the ice melts it's temperature will, in fact, stay the same (this was seen in an experiment done in class). The flat lines on a phase change graph show that during that period of time there was no change in temperature. The water is absorbing energy which is being converted into potential energy. This potential energy is used to change the water from one state of matter into another (solid - liquid - gas ). The graph shows that there are two types of energy being absorbed: kinetic and potential. The kinetic energy creates a change in temperature and is demonstrated in the sloping lines. When potential energy is absorbed is creates a change in the state of matter. The temperature will stay the same, hence the flat lines. The water will never absorb both kinetic and potential energy at the same time. Observe the graph above.

Calculate Q1, Q2, Q3

M x C x DT = Q

Q1:
394.5g x 4.184J/goC x 0 = 0 J

Q2:
394.5 x 4.184J/goC x 50 = 82529.4

Q3:
 394.5g x 4.184J/goC x 97 = 160107.036 J

Archer Fish: Snell's Law

The archer fish makes several instinctive calculations in order to catch its prey. These calculations are all to do with refraction from the air to the water. The archer fish must recognize the angle in which it will begin to shoot the water. Then it must calculation the angle of refraction in the air. The target is actually further away than it seems. The fish will have to direct its jet of water further away than the insect seems to be. It must calculate the angle of refraction. This is the angle that the fish must direct its jet of water (instead of straight up towards the target).

The calculations the fish must make are called "Snell's Law".
They look like this:
n1/n2 = Sinθ2/Sinθ1
n = refraction index
Sinθ= The angle of light

The fish instinctively uses this formula to calculate the angle of light in the air. This way it can locate the target's exact location.

Double Rainbow

Rainbows are the result of refraction and reflection of light by water droplets. White light enters the water droplet and is refracted, and then is reflected off the back of the droplet. Before leaving the drop the light is split into several different colors, or again refracted. This is how a single rainbow is formed.
A second rainbow is produced when there is an extra reflection of light in the water droplet. Some light is always lost in the droplet, and therefore the second rainbow will be lighter than the first.
The reason that a rainbow is circular is because it is the only shape that will reflect back to your eyes at 42o (53o for a secondary rainbow). No two people see the same rainbow. The rainbows shape and position in the sky all depends on the viewers location and the angle of the sun.

This video, "A History of the Universe in Sound" by Honer Harger explains how we can use sound to increase our understanding of the universe. First of all, one has to understand that space has sound. It is not silent. The sun, Jupiter, and the rings of Saturn all make sounds. The study of astronomical sounds is called radio astronomy. Scientists use sensitive antennas and receivers to capture the sound. One can discover many things about space (scale/size, age, what it's made of) from listening to its sounds. The oldest noise ever heard was picked up in 1965 at Bell Lab. This cosmic radiation is evidence that the Big Bang existed.

This video "Light on Dark Matter" by Patricia Burchat is an explanation on the mysteries of the universe; dark matter and dark energy. In this video Patricia explains that ordinary matter (humans, planet, stars etc) make up only 4% of the universe. 26% is made up of dark matter and the rest (70%) is made up of dark energy. Surrounding a galaxy and surrounding a cluster of galaxies is a gravitational force called dark matter. It is a cloud that has mass. Light is involved in this concept as well. When looking at a galaxy, through a telescope or naked eye, you may be seeing it in a different place than it actually is. This could be because a clump of dark matter is obstructing your view. The light from the galaxy is bouncing around this matter and entering your eye at a different angle. Therefore we may see the galaxy in a different place than where it actually is!
Space is growing bigger and bigger. The distance between galaxies is getting greater. Instead of expanding at a slower rate, the rate is actually increasing. The universe is expanding at faster rate than it did billions of years ago. Dark matter pulls matter further apart and encourages expansion. Dark energy decreases gravitational pull and puts more space between the galaxies.

My Favourite Type of Light

There are many different types of light. You have radio waves (low frequency) up to gamma rays (high frequency). If I had to chose one that I would not like to live without I would have to chose "visible light." Visible light are the colours we can see. This makes up only a small part of the electromagnetic spectrum. With wave lengths of 10 to the power of -6 meters, visible light lands right in the middle of the electromagnetic spectrum. Without visible light we would not be able to see colour or light. Our vision would be restricted to black shadows and shapes as our eyes adjusted to the darkness. I think visible light, although not so vital to other animals, is a neccessary part of our lives and we would be very different without it.

Doppler Effect

The situation going on in this video is called the "Doppler Effect." The Doppler Effect is when a siren or sound changes from a high pitch to a low pitch. The pitch of a sound is determined by the frequency. This frequency will change when the source of the wave is moving. Between the time that one sound wave and the next one are emitted, the source of the sound moves forward. The wave speed stays the same but the distance between the waves is shortened. This means the waves are at a higher frequency. Therefore the pitch appears to sound higher as the source travels away from you. In the video below, one can see how the waiter's version of the song is quite different from the original song (heard in the car). As the car passes by quickly, the waiter hears the music. Instead of hearing the actual pitch, he hears the pitch rising as the car travels further away. Therefore, his concept of the pitch of the song is different from the actual pitch.

Science Question 1:

"If a tree falls in the forest, and there's no one there to hear it, does it still make a sound?"

The falling of the tree will not make a sound, if there is no-one there to hear it. The tree falling will create vibrations and therefore cause sound waves. Unless there is a brain/ear to process the vibrations the falling of the tree will not make a sound. An eardrum and a brain needs to be present. These vibrations must be interpreted by a living person/animal. If not, the falling tree will not make a sound.