To implement this curriculum it is imperative to understand the physics concepts explored by the unit. In an attempt to understand this concepts I have written concise explanations about each of the topics in the unit. In addition, I will include any other concepts that may be needed to understand the concepts introduced.
Light (Department of Energy, 2003; Taylor, 1992).
Light is a wave of energy that does not need a medium to travel. It can travel as fast as 186,000 miles per second. It is a combination of electrical and magnetic energy that seems to travel faster than anything else does in the universe In fact light is so fast that even though the sun is so far from Earth it only takes solar light eight minutes to reach us. One interesting fact about light is that it slows down when traveling through substances such as glass, water, etc. There are several ways to think of light. The classical description says light is an electro-magnetic wave. This means that it is a varying electric and magnetic field, which spreads out or propagates from one place to another. It is not a physical substance. The modern quantum mechanical description says that light can also be considered to be particles called photons. These carry energy and momentum but have no mass. In both descriptions, the light energy is carried by a very real and observable mechanism Light can bounce, bend, refracts into many colors. It helps us see. Man has found ways to produce light but it is a phenomenon that is present in nature. The sun, our own star is an important source of light.
Sources of light (Kerrod & Holgate, 2002).
Light is present in many forms in nature from insects to our own star, the sun, we can see light all around us. Throughout history the humans have cherished light, first by worshiping it and later on by making light our selves. From striking stones to rubbing wood and later on striking metals. Friction is then a source of light that whether it is caused by nature of by humans the sparks that result from it can be use as a source of illumination. It is true that we not only have use light for illumination we also needed to keep warm. Our main source of light, the sun, it is perhaps one of the most important resources for life as we know it. It not only sheds light but it is a source of energy. Furthermore, many ancient civilizations worshiped the sun. But we find light in other natural sources such as: other stars and some plants and animals can make their own light. An interesting occurrence of light in nature is a flame that results from methane gas bubbles from rotting plants that rises to the ground surface and interacts with phosphine another gas from rotting animals. This chemical interaction produces a quickly moving flame when it interacts with air.
Due to its presence in nature and their need of energy and illumination, humans made the study and development of technology related to light a scientific endeavor. In ancient civilizations oil of different kinds were used to make lamps, torches, matches, and beeswax candles were invented. More recently, the incandescent light utilizes electricity and a filament to produce light. The interaction of atoms of a gas produces light in florescent light. In conclusion, this electromagnetic wave composed of tiny particles of energy called photons is an important resource.
Natural and artificial light, have much in common. Similar chemical reactions must be present for light to be produced. For example, the sun and an incandescent light bulb produce light when atoms are heated and release some of their thermal vibration as electromagnetic radiation. The difference is that one is present in nature and the other was invented and made by humans.
How can we make waves? (Smith, 1996).
A wave can be described as a disturbance that travels through a medium from one location to another location. One can observe how waves are form on water by applying disturbances such as throwing a pebble in a bucket; the rings formed in the water are waves. Such a demonstration may be useful in presenting this concept to students.
The Human Eye - Receptors
Our anatomy has equipped us to see light. Our vision requires an anatomical structure to perceive light. Although we can't in fact see light as it is due to its speed we posses the capacity to see some of it. Visible light is a complex phenomenon that needs to be explained taking into consideration both anatomy and physics. The fact is that light bounces and our eyes are capable to perceive that bouncing of a speedy phenomenon. Another fact is that for us to see the spectrum of light waves we need technology. Diffraction glasses, prisms, water and other materials or technology that slow down light allows us to see a truer picture of what light looks like.
Light and color (Burton & Taylor, 1998).
Light is similar to other electrical and magnetic energy or electromagnetic waves in that it has different wavelength. For example white light appears colorless but in fact it is composed of colors that have different wavelengths. When it travels fast it appears as white but when slow down one can see the different colors in it. A good demonstration of this would be to send a beam of white light through a prism one can see a spectrum of colors present in white light. This demonstration is present in nature when sunlight beams pass through drops of rain it forms a rainbow.
Reflection, light can bounce! (Burnie, 1992).
Because light bounces when it encounters an opaque surface we can control it and directed towards objects that allow it to bounce such as mirrors and other objects. Minerals such as metals create a reflection. This can be seen in the moon and how it reflects the sunlight. The reflection produce by the bouncing light makes object appear shiny.
Can light break? Refraction (Burnie, 1992).
It does not break in fact it bends, which is called refraction. Light travels through space very fast in a straight line but when it encounters transparent materials through which it can travel it slows down. Apparently light goes through transparent materials but as it slows down it bends; bending depends on the characteristics of the material through which the light ray travels. Another interesting way of slowing light is by introducing air at different temperatures. The speed difference
bends light rays. Depending on the temperature the light is bent by different amounts making it more visible. Perhaps you can remember when traveling in a highway how we can see it shimmering as if it was wet. What you see is a sunlight mirage cause by the difference in temperature. It works like this: the dark asphalt absorbs heat from sunlight and heats the air directly above it. Warm air directly above the road and cooler air above that form two layers of different temperature. Warm air is less dense than cold air and light travels faster in the thinner air, therefore light travels differently.
Lenses (Burnie, 1992; Glover, 2001).
Lenses are a way that inventors and physicist have manipulated refraction to utilize it in everyday life as well as in experimentation. Lenses are curved pieces of transparent materials that can refract light in a particular way. Lenses have been use to correct vision by changing the direction of the light rays; with concave lenses objects appear reduced. On the other hand you can see how the lens utilized in a lighthouse gives a strong beam of light because is a convex shaped piece of glass or clear plastic. In microscopes and telescopes, lenses collect light and focus it into the eye.
Light can bend, Optic Illusions (Kerrod & Holgate, 2002; Nature News Service / Macmillan Magazines Ltd 2002).
This bending effect can create optical illusions. The truth is that it is our brain that interprets what we see. Perception plays an important role in creating optical illusions. Utilizing color and lines we can create multiple illusions that will fool our brains into believing what we see even if it's not true. Illusions are then created by our brain as a coping mechanism to make sense of an image that is not fully understood. Einstein suggested that the force of gravity could bend light so that the gravity of planets and stars make them act as big lenses in the sky. In other words solid bodies in the space can in fact distort light waves. Recently a team of researchers, Sergei Kopeikin of the University of Missouri in Columbia and his colleague Edward Fomalont of the US National Radio Astronomy Observatory in Charlottesville, Virginia, used a network of radio telescopes in the United States and Germany to test this phenomenon. While looking at a quassar (a strong source of waves in the universe) near Jupiter they saw how the light appeared to come from another point in the space, thus showing that in fact the gravity of planets can make them act as lenses that bend light.
Shadows where is the light? (Richards, 1999).
Shadows are the silhouette of an object that is blocking the path of light. The shadows stretch away from the object and in opposite direction from the light. An object that does not allow light to travel through is called opaque. Examples of these objects are wood, rock, or our own bodies. Eclipses are the result of a shadow created either by the moon or the Earth blocking the sunlight. One very interesting phenomenon is how shadows could be use to tell time. From simple sighting to creating sundials the shadow and positioning of the sun in our sky can help us tell time.
How do cameras work? (Smith, 1996; Taylor, 1992).
Our eyes allow light to pass through an opening called pupil, the image then is projected inverted. A nerve called the optic nerve connects the retina with the brain. The camera is a light proof box that has a shutter, which prevent light from entering into the film chamber. Photographic cameras work with a photo sensitive (sensitive to light) film that allows for a picture to be imprinted. Other cameras like television cameras or camcorders allow the image to be processed in such a way that they can be projected similar to the eyes. Photography works by allowing light into the camera. Once the image is imprinted in the film we can then print them on paper.
What is energy? Light and electricity (Burnie, 1992; Kerrod & Holgate, 2002).
Lightning is a very interesting way of seeing the light that is produced by electricity in nature. A spark is produced by water and ice particles colliding and becoming charged by electricity. This amazing source of light is produced when an electric spark in the clouds makes the air ionized or so hot that it glows. Thus, lightning is a good example of a source of light due to heat. Another amazing process is the energy that plants absorb from the sunlight on a daily basis. Solar energy can also be used to power cars, telephones, calculators, water heaters, etc. Solar energy can be used as heat or by converting it to electricity.
What is physics?
Physics is the study of the nature of basic things such as motion, forces, energy, matter, heat, sound, and light. Physicists study a wide range of things. Black holes, atoms, engines, elevators, and baseballs all obey the laws of physics. Physics is about finding things out and understanding what lies behind every-day phenomena like rainbows, red sunsets and blue skies as well as the more revolutionary concepts of quantum theory, relativity, and cosmology. One of the key ideas in physics is that, behind the complexity of the world around us, there is an underlying simplicity and harmony in nature. Thus, physicists study nature to understand and manipulate the laws that govern it.
In conclusion the study of light is complex but extremely interesting. The explorations that this unit will bring about should not only teach my students science. In addition, it should allow for me to comprehend the processes necessary for me to teach such an abstract concept.