Mechanical waves are waves that require a medium. This means that they have to have some sort of matter to travel through. These waves travel when molecules in the medium collide with each other passing on energy.

Sound can travel through air,water or solids but it can't travel through vacuum . If you are curious about what is a vacuum, a vacuum is a  space in which there is no matter or in which the pressure is so low that any particles in the space do not affect any processes being carried on there.

-Electromagnetic waves are waves that can travel  through a vacuum. they don't need medium or electromagnetic waves to travel through electrical and magnetic fields that are generated by charge particles.

EXAMPLES:

Light Waves
- Light waves are forms of moving energy made of tiny microscopic particles called photons. Scientists usually refer to light waves as electromagnetic waves because they make up what is known as the electromagnetic spectrum.

Heat Waves
- Radio waves have the longest wavelengths in the electromagnetic spectrum. They range from the length of a football to larger than our planet. Heinrich Hertz proved the existence of radio waves in the late 1880s.

X-Ray Waves
- X-rays are types of electromagnetic radiation probably most well-known for their ability to see through a person's skin and reveal images of the bones beneath it. Advances in technology have led to more powerful and focused X-ray beams as well as ever greater applications of these light waves, from imaging teensy biological cells and structural components of materials like cement to killing cancer cells.  

 Period
- The amount of time it takes for a molecule on a medium to complete one vibrational loop. A period is a unit of time that is measured in seconds, hours, days, or years.
- The term "period" refers to the amount of time it takes to complete a task. When an event repeats itself, we call it repetitive and refer to the time it takes for the event to replicate itself as the duration.

 Velocity
- Velocity is often used to refer to distance, but it also refers to both speed and direction.
- The sum of a wave's wavelength and frequency (number of vibrations per second) is its velocity, which is independent of its intensity.

- The loudness depends on the amplitude of the vibration. It will be louder when the amplitude is high. Suppose when we pluck a string of the sitar it starts vibrating with low amplitude and if we apply more energy by plucking more strongly, the string will vibrate with the greater amplitude and produce a loud sound. As the amplitude of vibration increases, sound also increases.

Trough - A wave's trough is the location on the medium where the greatest amount of negative or downward displacement from the rest position can be seen.

Amplitude - The maximum amount of displacement of a particle on the medium from its rest location is referred to as the amplitude of a wave.

Wavelength - The length of one full wave cycle is the wavelength of a wave. If you trace your finger over the wave in the diagram above, you'll find that it follows the same path every time.

        - Wave movement in the sea                 - Mexican wave in a sports arena

        - Vibrations when playing a  guitar           - Using a Microwave that forms radiation

Application of TIR
- Optical fibres also use total internal reflection. An optical fibre has a high-refractive-index inner core that is surrounded by a lower-refractive-index outer cladding.
- Light can propagate down the fibre in a zigzag direction, through a sequence of absolute internal reflections, when it is inserted into the inner core at one point.
- Optical fibres are useful for bringing light to areas that are otherwise unavailable. They have a wide range of practical uses. Fiber optic imaging instruments in medicine and fiber optic cables in telecommunications are examples of this.
- A fibre optic cable is used to create an endoscope. Doctors use it to examine the interior of the human body, such as the stomach and duodenum.
- Copper cables are being phased out of the telephone system in favor of fiber optic cables.
- Using pulses of light from a laser, multiple signals may be transmitted at high speeds via bundles of fibres.

Compression - The highest density point on a medium through which a longitudinal wave is moving.

Wavelength - The length of one full wave cycle is the wavelength of a wave. If you trace your finger over the wave in the diagram above, you'll find that it follows the same path every time.

Example of Longitudinal Wave
- Earthquake (Seismic-P Wave) - Tsunami Waves
- Clapping and Stamping                 - Vibrating Mobile Phone when ringing
- Sound and Ultrasound Wave

X-Rays (Wavelength 10-8 to 10-12 meters)
- X-rays range in wavelength from 0.01 – 10 nm and are principally created by super-warmed gas from detonating stars and quasars. It is able to go through various sorts of materials.
- X-rays are generally utilized for clinical imaging and for reviewing freight and gear. Like gamma beams, the Earth's environment blocks x-rays radiation.
- The Medica instruments to view bone structure. 

Ultraviolet (UV) (Wavelength 10-7 - 10-8 meters)
- Ultraviolet (UV) light has a wavelength of around 1 – 380 nm. Sun is the source of ultraviolet energy. 
- The UV portion of the spectrum is partitioned into UV-A, UV-B, and UV-C. UV-C rays are the most destructive and are totally consumed by our climate. UV-B rays are hurtful rays that cause burn from the sun. In spite of the fact that UV waves are imperceptible to the natural eye, a few creepy crawlies, like honey bees, can see them.
- It is useful in the study of galaxies. 

Waves Sound - that results from the back and forth vibration of the particles of the medium through which the sound wave is moving

Seismic Waves - are waves of energy that travel through Earth's layers, and are a result of earthquakes, volcanic eruptions, magma movement, large landslides and large man-made explosions

 
- Acoustics is the science of the production, control, transmission, reception and effects of sound and the phenomenon of hearing. According to Science, sound waves can travel through other materials besides air. The speed of its travel depends on the density of the medium. Sound has characteristics that are separated into three: amplitude, loudness and intensity. Sound can be measured with a decibel scale. The highness or lowness of a sound which depends on frequency of sound waves is pitch. A study called Doppler Effect is a change in frequency and wavelength of a sound was produced by a source. 

- Optics is the branch of physics that studies the behavior and properties of light, including its interactions with matter and the construction of instruments that use or detect it. There are two models of light. A ray is a straight line segment weather arrow on one end Indicating the direction in which light is traveling. Properties that are explained using the Ray approximation for light fall under geometric or Ray optics. Properties that consider light as a wave are at the realm of physical or wave optics. Speed of light,  Rectilinear propagation of light, Illumination and the Inverse Square Law, Mirrors are few studies under Optics.

- Process and different fields of LASER Applications.

https://www.physics-and-radio-electronics.com/physics/laser/applicationsoflasers.html

- Importance of LASER Applications.

- Laser technology is very important in the modern world because it is used in many fields. Lasers are also used in DNA sequencing instruments, surgery hair removal products and skin treatments. The incredible uses of laser technology include: barcode scanners, laser printers, optical disk drives, cutting and welding materials, semi-conducting chip manufacturing, law enforcement devices, and free-space optical communication.

- Surface waves are a type of mechanical wave that travels along a surface or in between differing media The particles of these waves travel both up and down, and back and forth in this case, causing it to move in a circle. Surface waves also produce two types; Rayleigh waves and Love waves. Rayleigh waves travel near solid surfaces and include both longitudinal and transverse motions that decrease amplitude as the surface increases. On the other hand, Love waves or Q waves move in a horizontal path that makes the surface move side to side. It also moves faster than Surface waves.

- The infrared segment of the spectrum goes from roughly 0.75 µm to 100 µm (750 nm - 10,000 nm) in wavelength.
- It is divided into three main regions, Near Infrared (NIR): 0.7 – 1.3µm, Shortwave Infrared (SWIR): from 1.3 – 3 µm and the Far or Thermal Infrared from 3 - 100 µm.
- Infrared radiation is utilized widely in far-off detecting. Items reflect, communicate, and retain the Sun's close infrared and shortwave radiation interestingly and this can be used to notice the wellbeing of vegetation, soil organization, and dampness content.
- The region from 8 to 15 µm is alluded to as warm infrared since these frequencies are best for contemplating the longwave nuclear power emanating from the Earth. It used in remote control and imaging applications. 

 Amplitude 
- The amplitude (signal strength) of the carrier wave is varying in relation to that of the message signal, such as an audio signal, in amplitude modulation.
- For a transverse wave, the maximum displacement of some point on the string from its direction while the string is at rest is used to calculate the amplitude of a wave on a plucked string, for example.
- For a longitudinal wave, the maximum displacement of a particle from its equilibrium state, such as a sound wave, is used to calculate amplitude. The amplitude of a wave is said to be damped as it gradually reduces as its energy is lost.. 

Wavelength
- The frequency of a wave is directly proportional to its energy, but the wavelength is inversely proportional. That is to say, the higher the energy, the higher the frequency and shorter the wavelength. Short wavelengths are more energetic than long wavelengths due to the interaction between wavelength and frequency.
- Typically, the wavelength of transverse waves is determined from peak to crest or from trough to trough. It is measured from compression to compression or from rarefaction to rarefaction in longitudinal waves.

Radio Waves ((Wavelength >10-1meters)
- Radio waves have the longest wavelengths in the electromagnetic spectrum with wavelengths going from around 1mm to a few hundred meters. 
- Radio waves are utilized to communicate an assortment of information. Remote systems administration, TV and novice radio all utilization radio waves. The utilization of radio frequencies is typically directed by governments. 
- It is used for communication. 

- Animals like bats and dolphins use high-frequency sounds to see their surroundings, listen to the sound reverb from the environment, and create a mental picture of where they are. Nowadays, many blind people are learning to do the same thing as dolphins, by clicking on their tongues and listening to reverberations. There are already many teachers and instructors of the new method who show other blind people how to pick up the basics of echolocation and thus become more independent.

- People use the principles of echolocation to locate objects underwater. During World War I, scientists developed instruments that used sound waves to locate enemy submarines. Instruments that use echolocation to locate objects are known as Sonar stands for sound navigation and ranging. The sonar machines could detect sounds coming from submarine propellers. Sonar devices could also send out ultrasound waves and then use the echoes to locate underwater objects. The information from the echoes could then be used to form an image on a screen. Later, people found many other uses for sonar. Fishing boats use sonar to find schools of fish. The oceanographers who study the ocean, use it to map the seafloor. People have even used sonar to find ancient sunken ships in deep water.

Quality/Timbre
- It is a characteristic of sound that allows us to recognize the difference between sounds of similar loudness and pitch. The waveform of a sound is what determines its quality. It's enjoyable to listen to high-quality sound. The instruments are of different shapes and sizes, and they produce different loudness harmonics, so their sound can be distinguished easily.

The number of seconds per waveform, or the number of seconds per oscillation, is called the Time Period (T). The reciprocal relationship between frequency and time is obvious.

So frequency,

So frequency,