The Nature of Waves

A wave is any disturbance that transmits energy through matter or empty space. Most waves transfer energy by the vibration of particles in a medium. A medium is a substance through which a wave can travel. Waves that need a medium are called mechanical waves. Some waves transfer energy without going through a medium. Visible light is one example.


Types of Waves
All waves transfer energy by repeated vibrations. However, waves can differ in many ways.The two main types of waves are transverse waves and longitudinal  waves. Sometimes, a transverse wave and a longitudinal wave can combine to form another kind of wave called a surface wave.

Transverse Waves
Transverse means "moving across." Waves in which the particles vibrate in an up-and-down motion are called transverse waves. The particles in this kind of wave move across or perpendicularly to, the direction that wave is going. The highest point of a wave is called a crest, and the lowest point between each crest is called a trough, EM waves (electromagnetic waves) are considered transverse waves.


Longitudinal Waves
In a longitudinal wave, the particles of a medium vibrate back and forth along the path that the wave moves. A part of a longitudinal wave where the particles are crowded together is called a compression. A part where the particles are spread apart is called a rarefaction.

Sound Waves
A sound wave is an example of a longitudinal wave. Sound waves travel by compressions and rarefactions of air particles.


Combination of Waves
When waves form at or near the boundary between two media, a transverse wave and a longitudinal wave can combine to form a surface wave.The particles move forward at the crest of each wave and move backward and through.

Properties of Waves

Amplitude is the maximum distance that the particles of a wave’s medium vibrate from their rest position. A larger amplitude carries more energy than a wave with a small amplitude.

Wavelength is the distance between any two crests or compressions next to each other in a wave. The distance between two troughs or rarefactions next to each other is also a wavelength. The shorter  wavelength carries more energy than the wave with a longer wavelength. 

Frequency is the number of waves produced in a given amount of time. Frequency is expressed in hertz. in waves, one hertz is equal to one wave per second.

Wave Interactions

Reflection happens when a wave bounces back after hitting a barrier. all waves can be reflected. A reflected sound wave is called an echo.  Waves are not always reflected when they hit a barrier. A wave is transmitted through a substance when it passes through the substance.

Refraction is th bending of wave as the wave passes from one medium to another at an angle. When a wave moves from one medium to another, the wave's speed changes.

Diffraction is the bending of waves around a barrier or through an opening. Most of the time, waves travel in a straight line, but in some circumstances waves bend or curve when they reach the edge of an object, thus diffraction happens.

Interference

     is the combination of two or more waves that result in a single wave.

Constructive Interference happens when the crests of one wave overlap the crests of another wave or waves. The troughs of the waves also overlap. The result is a new wave that has a higher crests and deeper troughs than the original wave had.

Destructive Interference happens when the crests of one wave and troughs of another wave overlap. The new wave has smaller amplitude than the original waves had.

Standing Wave is a pattern vibration that simulates a wave that is standing still. a standing wave only looks as if its standing still.

Resonance is a phenomenon that occurs when two objects naturally vibrate at the same frequency; the sound produced by one object causes the other object to vibrate. A resonating object absorbs energy from the vibrating object and vibrates, too. 

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

.

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.