Light

What is light?

Light is a type of energy that travels as a wave. Light is different from other waves because light is an electromagnetic wave. This is a wave that can travel through empty space or matter and consists of changing electric and magnetic field.
Electric field surrounds every charged object.  It pulls the objects that are like charges away, and pulls oppositely charged objects together. A magnetic field surrounds every magnet. It attracts all objects that contain iron.

How are EM Waves Produced?

EM waves are produced by the vibration of an electrically charged particle. When the particle vibrates, the electric field around it also vibrates, thus, a magnetic field is created.The vibration of both fields together produce an EM wave.The transfer of energy as EM waves is called radiaton.

Electromagnetic Spectrum

Characteristics of EM Waves

The entire spectrum of EM waves are called electromagnetic spectrum. It is divided into regions according to the length of the waves. There is no sharp divisions between one kind of wave and the next, some have overlapping ranges.

Microwaves have shorter wave lengths and higher frequencies than radiowaves do. Microwaves are used to send signals to other objects like cellphones and satellites.
Radars use microwaves to detect the speed and location of objects.
Infrared waves are not visible but can be detected by some devices.

What is Visible Light?

Visible light is the very narrow range of wavelengths and frequencies in the EM spectrum that humans can see. Some of the energy that reaches the earth from the sun is visible light. White light is visible light of all wavelengths combined.

Ultraviolet light is another type of EM wave produced by the sun. They affect our bodies in both good and bad ways.

Bad Effects: Too much UV light can cause
* sunburn
*wrincles, and eye damage
*skin cancer

Good Effects:
*UV lamps are made to kill bacteria on food and surgical tools.
*When exposed to UV light, skin cells produce vitamin D

X Rays and Gamma Rays

X rays can be useful in the medical field, but too much exposure can kill living cells. X ray machines are also used as security devices in airports and other public buildings. These allow officers to see inside the bags and other containers without opening them.

Gamma rays are used to treat some forms of cancer. These are also used to kill harmful bacteria in foods such as meat and fresh fruits

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Interactions of Light Waves

Reflection happens when light waves bounce off an object. The Law of Reflection states that the angle of incidence is equal to the angle of reflection. Incidence is the arrival of a beam of light at a surface.

 
Types of Reflection:

*Regular Refelction- when beams are reflected at the same angle.
*Diffuse Reflection- when beams reflect at many different angles.

Diffraction

Absorption is the transfer of energy carried by light waves to particles of matter. Scattering is an interaction of light to change direction. Refraction is the bending of a wave as it passes at an angle from one substance, or material, to another.Diffraction is the bending of waves around barriers or through openings. Interference is a wave interaction that happens when two or more waves overlap. Overlapping waves can aombine by:

*Constructive Interference- the resulting wave has greater amplitude, or height, than the individual waves had. These can be seen when light of one wavelength shines throught two small slits onto a screen.

*Deconstructive Interference- the resulting wave has smaller amplitude than the individual waves had.

Light and Color

Transmission is the passing of light through matter.

Types of matter:
*Transparent- They allow light to pass through little interference. Eg: clear glass
*Translucent- it transmits light, but also scatters it as it passes through. Eg: wax paper.
*Opaque- it is not transparent or translucent. It does not transmit any light. Eg: wood

Colors of objects are determined by the wavelengths of light that reach your eyes. ROY G. BiV (red, orange, yellow, green, blue, indigo, violet) are the colors that make up the rainbow.