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Waves

In physics, a wave is the propagation of energy (not mass) in space due to a disturbance in one of its physical properties, such as density, pressure, electric field, or magnetic field. This phenomenon can occur in empty space or in space containing matter (air, water, earth, etc.).

Waves are produced as a consequence of oscillations and vibrations of matter, which propagate over time as described by Wave Theory, the branch of physics dedicated to understanding this phenomenon, which is extremely common in the universe.

The effects of their appearance and characteristics will depend on the origin of the waves or the nature of the medium through which they propagate. Thus, we can talk about light waves, sound waves, etc., each with different physical properties and frequencies, depending, among other things, on the medium in which they propagate and how much energy they carry.

Some waves, such as sound waves, cannot be transported in a vacuum; they require a physical medium. Others, such as electromagnetic waves, can do so perfectly and quickly: this is how artificial satellites operate, relaying information to Earth via microwaves.

Types of waves

Waves are classified according to different criteria

According to the medium in which they propagate

Mechanical waves. These require an elastic medium (liquid, gaseous, or solid) and specific temperature and pressure conditions to propagate effectively. For example: sound waves that propagate through air or water.

Electromagnetic waves. These do not require a medium because they can propagate in a vacuum. For example, light.

Gravitational waves. Alterations in space-time (recently confirmed by science).

Electromagnetic waves

According to their periodicity

Periodic waves. They present repetitive cycles.

Non-periodic waves. They exhibit irregular cycles.

Periodic waves

According to their direction

One-dimensional waves. They propagate through a single dimension in space.

Two-dimensional waves. They propagate through two dimensions and are also often called surface waves.

Three-dimensional waves. They propagate in three dimensions and are often called spherical waves.

Ocean waves and drops are two-dimensional waves

According to the movement of the medium

Longitudinal waves. The particles in the medium move in the same direction as the wave's propagation.

Transverse waves. The particles vibrate perpendicular to the direction of the wave's propagation.

Parts of a wave

Crest. This is the maximum point in the wave.

Trolley. This is the lowest point of a wave (the opposite of the crest).

Period. This is the time it takes for the wave to travel from one crest to the next, that is, to repeat itself. It is represented by the letter T.

Amplitude. It represents the maximum variation in displacement, the vertical distance between the crest and the midpoint of the wave. It is represented by the letter A.

Frequency. It is the number of times the wave repeats in a given unit of time, which is why it is calculated according to the formula f = 1/T. It is represented by the letter f.

Wavelength. It is the distance between two consecutive crests of the ripple. It is represented by the symbol λ (lamda).

Cycle. It is the complete ripple, from beginning to end.

How do waves propagate?

Waves usually require a material medium to propagate, although some can propagate perfectly well in a vacuum (depending on the nature of the wave).

For example, electromagnetic waves, which are oscillations of electric and magnetic fields and travel at the speed of light, do not require a material medium to propagate.

On the other hand, mechanical waves require a physical medium. propagate, such as water, metal, or air. For example, when we throw a stone into a pond, the stone causes a ripple that propagates through the water.

Activity. Answer the following questions.

Remember to review the answers to the open-ended questions at the bottom of this page.

1. What is the lowest point of a wave?

2. What is the part where the maximum variation in displacement occurs?

3. What is an example of electromagnetic waves?

4. Ocean waves are examples of waves...

5. How are waves produced?

Once you click this button, the questions will close and you will not be able to change your answer.

6. What is a wave?

7. What is the frequency formula (f = 1/T) used for?

8. What branch of physics studies waves?

9. Longitudinal and transverse waves are classified according to...

10. What do mechanical waves need to propagate?

Still have questions?

We recommend visiting the following materials for further knowledge or understanding on the topic:

Answers to open questions:

6. It is the propagation of energy in space due to the disturbance of one of its physical properties.

7. To measure the number of times a wave repeats itself in a given unit of time.

8. Wave Theory

9. The motion of the medium

10. A physical medium

References:

1. Leskow, E. C. (2025, 25 marzo). Onda - Concepto, tipos, partes y cómo se propaga. Concepto. https://concepto.de/onda-2/

2. The Editors of Encyclopaedia Britannica. (2025h, abril 25). Wave | Behavior, Definition, & Types. Encyclopedia Britannica. https://www.britannica.com/science/wave-physics

3. Admin. (2023b, abril 25). Wave. BYJUS. https://byjus.com/physics/waves/

4. Physics Tutorial: What is a Wave? (s. f.). https://www.physicsclassroom.com/class/waves/Lesson-1/What-is-a-Wave

5. Cognito. (2020b, enero 15). GCSE Physics - Intro to Waves - Longitudinal and Transverse Waves [Vídeo]. YouTube. https://www.youtube.com/watch?v=aCu4VRKMstA

6. CrashCourse. (2016b, julio 28). Traveling Waves: Crash Course Physics #17 [Vídeo]. YouTube. https://www.youtube.com/watch?v=TfYCnOvNnFU

7. FuseSchool - Global Education. (2017c, diciembre 20). Wave Motion | Waves | Physics | FuseSchool [Vídeo]. YouTube. https://www.youtube.com/watch?v=CVsdXKO9xlk