"Light Wave"

Light and sound travels in a medium as a wave. It is very intriguing to dig out information about it and know how it works and how it affect or benefit us, humans. Our technologies today are the main example of how this wave work and benefit us in everyday life. To know more of light wave we should study first what is wave. Wave is undulating motion; a movement through, or over the surface or along the edge of something that is similar in its appearance or effects to a wave.

Waves are divided into types according to the direction of the displacements in relation to the direction of the motion of the wave itself. If the vibration is parallel to the direction of motion, the wave is known as a longitudinal wave. The longitudinal wave is always mechanical because it results from successive compressions (state of maximum density and pressure) and rarefactions (state of minimum density and pressure) of the medium. Sound waves typify this form of wave motion. Another type of wave is the transverse wave, in which the vibrations are at right angles to the direction of motion. A transverse wave may be mechanical, such as the wave projected in a taut string that is subjected to a transverse vibration; or it may be electromagnetic, such as light, X ray, or radio waves. Some mechanical wave motions, such as waves on the surface of a liquid, are combination of both longitudinal and transverse motions, resulting in the circular motion of liquid particles.

 

 LONGITUDINAL WAVE 

   

TRANSVERSE WAVE

For a transverse wave, the wavelength is the distance between two successive crests or troughs. For longitudinal waves, it is the distance from compression to compression or rarefaction to rarefaction. The frequency of the wave is the number of vibrations per second. The velocity of the wave, which is the speed at which it advances, is equal to the wavelength times the frequency. The maximum displacement involved in the vibration is called the amplitude of the wave.

Light wave is an electromagnetic wave which originates in the vibrations of electrons. Light wave has a higher frequency than radio waves but radio waves can be considered as low-frequency light wave. The lowest frequency our eyes can see is perceived by our brain as the color red, and the highest is violet. Still higher frequency is ultraviolet and beyond this are the x-ray and gamma-ray region. In vacuum all waves travel in the same speed but they differ in frequency. The classification of electromagnetic waves according to frequency is the electromagnetic spectrum.

  

 ELECTROMAGNETIC SPECTRUM

Properties of light waves are; diffraction, interference and polarization. Diffraction is property of wave motion, in which waves spread and bend as they pass through small openings or around barriers. Diffraction is more pronounced when the opening, or aperture, or the barrier is similar in size to or smaller than the wavelength of the incoming wave. Diffraction is a property of the motion of all waves. For example, if a radio is turned on in one room, the sound from the radio can be heard in an adjacent room even from around a doorway. Similarly, whenever water waves pass an object on the surface of the water, such as a jetty or boat dock, waves that pass the object's edge spread out into the region behind the object and directly blocked by it.

 

Interference is a property of wave that that occurs when two or more waves overlap or intersect. When waves interfere with each other, the amplitude of the resulting wave depends on the frequencies, relative phases (relative positions of the crests and troughs), and amplitudes of the interfering waves. Interference can occur with all types of waves, not only with light waves. Some of the wavelengths interfere constructively, and other wavelengths interfere destructively. For an instance, we can observe that a bubble appears rainbow colored. It is because of the different wavelengths of light correspond to different colors; the light reflecting off the soap bubble appears colored.

Polarization is another property of wave that the alignment of the transverse electric vectors that make up electromagnetic radiation. Such waves of aligned vibrations are said to be polarized. Polarization is important in wireless communications systems. The physical orientation of a wireless antenna corresponds to the polarization of the radio waves received or transmitted by that antenna. Thus, a vertical antenna receives and emits vertically polarized waves, and a horizontal antenna receives or emits horizontally polarized waves. The best short-range communications is obtained when the transmitting and receiving (source and destination) antennas have the same polarization.

 

See, how amazing waves can be ! ;)

"Technologies With the Influence of Light"

Today, thanks to our very patient scientists in the whole world, that give their valuable time putting their knowledge about light into new technology that will help and benefit us reach the increasing demand of people. As our generation goes on we have observed that we are very dependent on technology. The main reason why we depend on them is that, we people want to live in the easiest way we can. We want an instant solution in our problems. Light plays a very vital role especially in our technology today. Scientists have developed technology with the help of light. LED Christmas lights, lasers, fiber optics, telescopes are just some of these technologies.

LED (Light Emitting Diode) Christmas lights are quickly gaining popularity it is because of their low usage of energy and last long. Light Emitting Diode is a device that emits visible light or infrared radiation when an electric current passes through it. LEDs are made of semiconductors, or electrical conductors, mixed with phosphors, substances that absorb electromagnetic radiation and reemit it as visible light. When electrical current passes through the diode the semiconductor emits infrared radiation, which the phosphors in the diode absorb and reemit as visible light.

Laser on the other hand, is a device that produces and amplifies light. The word laser is an acronym for Light Amplification by Stimulated Emission of Radiation. Laser light is very pure in color, can be extremely intense, and can be directed with great accuracy. Lasers are used in many modern technological devices including bar code readers, compact disc (CD) players, and laser printers. Lasers can generate light beyond the range visible to the human eye, from the infrared through the X-ray range. Laser can be used in the field of medicine to cut and cauterize certain body tissues in a small fraction of a second without damaging surrounding healthy tissues. Lasers have been used to “weld” the retina, bore holes in the skull, vaporize lesions, and cauterize blood vessels. Laser surgery has virtually replaced older surgical procedures for eye disorders. Not only in medicine that a laser can be used, it can also be used in industry for precisely heat, melt, or vaporize material. It is also ideal for space communication and be used for military purposes.

Fiber optics is a technology that uses strands of glass, called optical fibers, to channel light. Total internal reflection holds light within a glass fiber no matter how much the fiber is bent, and pulses of light can be used to carry telephone and data signals many kilometers through fiber-optic cables. Surgeons use fiber optics to look inside lungs and other body cavities. Tools called, endoscopes have one bundle of optical fibers that leads light to the tip of the endoscope; a second bundle carries an image back.

Telescopes are also one of the technologies that exist with the science of light. Infrared telescopes use the basic design of an optical reflecting telescope, but have a detector at the focus that sees only infrared light. Because heat produces infrared radiation, the signal that an infrared telescope receives can be contaminated by the heat of the atmosphere if the telescope is Earth-based, as well as by the heat produced by the telescope itself. To adjust for this contamination, telescopes often take frequent readings of the background radiation away from the object being observed. The background radiation is then subtracted from the final image of the observed object. Infrared telescopes are also cooled to very low temperatures to reduce heat contamination of the image.

Computed Tomography, also known as computed axial tomography, or CT scan, medical technology that uses X rays and computers to produce three-dimensional images of the human body. Unlike traditional X rays, which highlight dense body parts, such as bones, CT provides detailed views of the body’s soft tissues, including blood vessels, muscle tissue, and organs, such as the brain. While conventional X rays provide flat two-dimensional images, CT images depict a cross-section of the body. A patient undergoing a CT scan rests on a movable table at the center of a donut-shaped scanner, which is about 2.4 m (8 ft) tall. The CT scanner contains an X-ray source, which emits beams of X rays; an X-ray detector, which monitors the number of X rays that strike various parts of its surface; and a computer. The source and detector face each other on the inside of the scanner ring and are mounted so that they rotate around the rim of the scanner. Beams from the X-ray source pass through the patient and are recorded on the other side by the detector. As the source and detector rotate in a 360° circle around the patient, X-ray emissions are recorded from many angles. The resulting data are sent to the computer, which interprets the information and translates it into images that appear as cross-sections on a television monitor. By moving the patient within the scanner, doctors can obtain a series of parallel images, called slices.

There are many technologies that exist with the help of science; these are just few of them. It is amazing to know how light can be very useful to us, not just by making new technology for us to live life easier, for us to explore the wonder and mystery of the world but most importantly for giving us life.

Properties Of Light

There are many things that we do not know about light. We are not aware in its work and sometimes ignore its wonderful effect in our environment and our life. Maybe because we are not curios enough to take time and explain why such things happen or we are too much busy in our life that we don’t care in some simple admirably things that happens every day. Today, as I studied light I was surprise to know that there are still many things about light I don’t know and it is more becoming very interesting. 


Light can be scattered, reflected, refracted and diffracted. Solid substances that scatter light are said to be translucent. Transparent materials, such as glass, allow light to pass through them without scattering, so a clear image can be seen. Reflection also occurs when light hits the boundary between two materials. Some of the light hitting the boundary will be reflected into the first material. The very common example is when we look at the mirror, the image we see is identical of our appearance but with left and right reversed. Refraction on the other side is the bending of light when it passes from one kind of material into another. Diffraction happens when light passes through a slit with a size that is close to the light’s wavelength, the light will diffract, or spread out in waves.

As we observe in the video above, we saw how light can be reflected, refracted, scattered, and diffracted of dispersed. First in reflection, we observed that the re-emitted light bounces back into the medium from which it came. Another good example on this phenomenon is our reflection in the mirror. We can see the image exactly the same size of our image, exact color, size and even distance but it shows lateral inversion of our image. Reflection is governed by the “law of reflection” which states that the angle of reflection is equal to the angle of incidence.

Regular reflection (in which the direction of the reflected wave front is sharply delineated) is governed by the law that both the incident, or striking, rays and the reflected rays travel in directions making equal angles with the normal, a line perpendicular to the reflecting surface at the point of incidence; and that the rays lie in the same plane as the normal. These angles are called the angle of incidence and the angle of reflection. Rough surfaces reflect in many directions, and such reflection is called diffuse.

Refraction in other hand is the change of direction of the wave that occurs when wave of energy such as light passes from one medium to another of a different density. As above shown the laser bend and go with the flow of the water.

Dispersion of light is the separation of visible light or other electromagnetic waves into different wavelengths.  We can observe it when a prism is hit by light. It will disperse spectrum of colors. It is also the reason why we can see rainbow in the sky.

Scattering is different from reflection, where radiation is deflected in one direction, some particles and molecules found in the atmosphere have the ability to scatter solar radiation in all directions. The particles/molecules which scatter light are called scatterers and can also include particulates made by human industry. Scattering is a general physical process where some forms of radiation, such as light, sound, or moving particles, are forced to deviate from a straight trajectory by one or more localized non-uniformities in the medium through which they pass. In conventional use, this also includes deviation of reflected radiation from the angle predicted by the law of reflection. Reflections that undergo scattering are often called diffuse reflections and unscattered reflections are called specular (mirror-like) reflections.

What is Light?

Light plays a very important role in our everyday life. Without light life maybe impossible to observe in our planet. Imagine life without light, our planet Earth will be dark and dead. We are very grateful that we have the sun, as our source of light. Without light we cannot see the beauty of mother Earth. During the day, sunlight provides heat and light which are two types of energy. This is the reason why life exists on Earth. Light helps plants to grow on land and in the sea, providing food for Earth’s animal life. Heat energy keeps the Earth at a suitable temperature for life to exist.

Light is a form of energy visible to the eye. Nothing travels faster than light. As we observe in our weather we can see lightning first before hearing the sound of thunder. Its speed in a vacuum is about 300,000 kilometers per second, but it travels slightly slower through materials such as air, glass or water. Light travels from its sources as a series of electromagnetic waves. Scientist draw arrow-shaped lines called rays to show the direction of travel these light waves. When an object is placed in a beam of light, the object casts a shadow that matches its own shape. This is because light travels in straight lines through space.

The earliest speculations about light were hindered by the lack of knowledge about how the eye works. The Greek philosophers from as early as Pythagoras, believed light issued forth from visible things, but most also through vision as distinct from light, proceeded outward from the eye. Some early ideas of Greeks however, were correct. The philosopher and state man Empedocles believed that light travels with finite speed. The philosopher and scientist Aristotle accurately explained the rainbow as a kind of reflection from raindrops. The mathematician and astronomer Ptolemy was the first person on record to collect experimental data on optics. Through logic and experimentation the Egyptian scientist Ibn Al Haythen he finally discounted Plato’s theory that vision issued forth from the eye. His work influenced all later investigation on light.

We should be very thankful to all the scientist and philosophers that studied out light, because of them we may appreciate light and predict it's cause.