1. What Reflection of Waves Means
Reflection happens when a wave hits a barrier and bounces back into the same medium. Instead of passing through the obstacle, the wave turns around and travels in the opposite direction.
I like to think of reflection as a wave ‘reversing its path’ when it cannot continue forward.
2. Definition of Reflection
Definition: Reflection of waves is the phenomenon in which a wave strikes a surface or boundary and returns to the original medium.
The wave may flip, change direction, or change shape depending on the boundary.
3. How Reflection Happens
When a wave reaches a boundary, some or all of its energy may be sent back. What happens depends on the nature of the boundary:
- Rigid boundary: the wave reflects and inverts (crest becomes trough and trough becomes crest).
- Free boundary: the wave reflects without inversion.
Although the direction changes, the wave still travels in the same medium after reflection.
3.1. Example of Rigid Boundary
If you send a pulse along a fixed rope, the pulse reflects and comes back upside down. This happens because the fixed end cannot move, so it exerts an equal and opposite force.
3.2. Example of Free Boundary
If the rope end is loosely attached or allowed to move, the reflected pulse returns without flipping.
4. Reflection of Sound Waves
Sound waves also reflect from surfaces. Hard and smooth surfaces like walls and cliffs reflect sound strongly. This is why we hear echoes.
4.1. Echo Example
When you shout in a large empty hall or near a mountain, the sound reaches the wall or cliff and returns to your ears as an echo. The sound wave is simply reflecting back to you.
5. Reflection of Light Waves
Light also undergoes reflection. Mirrors, shiny metals, and smooth surfaces reflect light cleanly, allowing us to see images.
5.1. Simple Picture
Light ray hits a mirror → bounces back → reaches the eyes → forms an image. The basic idea is the same as any wave reflecting from a boundary.
6. Important Terms in Wave Reflection
When we describe wave reflection, a few terms help explain the process clearly:
- Incident wave: the wave that strikes the boundary.
- Reflected wave: the wave that returns after striking the boundary.
- Point of incidence: the point where the wave meets the boundary.
These terms make it easy to sketch and analyze wave behaviour.
7. Laws of Reflection (Simple Form)
Reflection of waves follows the same rules whether it’s sound, light, or a ripple on water:
- The angle of incidence equals the angle of reflection.
- The incident wave, reflected wave, and normal all lie in the same plane.
This geometric behaviour makes reflection predictable and easy to study.
8. Examples of Reflection in Real Life
Reflection appears in many everyday situations:
- Echoes in large halls or empty streets.
- Reflection of light in mirrors.
- Ripples in water bouncing back from the side of a container.
- Reflection of waves along a stretched string.
All these examples follow the same basic idea — the wave hits a boundary and returns to its medium.
9. Why Reflection Is Important
Reflection is essential for understanding echoes, optical instruments, musical acoustics, sonar technology, and even wave behaviour in physics labs. Once the idea of waves bouncing back becomes clear, many wave-related concepts become much easier to understand.