Reflection
* Speed remains the same. When a wave reflects off a surface, it bounces back. The speed of the wave in the original medium doesn't change. The direction of propagation changes, and the wave might experience a phase shift depending on the nature of the reflecting surface.
Refraction
* Speed changes. When a wave moves from one medium to another (e.g., from air to water), it changes speed. This is because the wave's speed is determined by the properties of the medium. The change in speed causes the wave to bend, which is the phenomenon of refraction. The amount of bending depends on the angle of incidence and the difference in speeds between the two media.
Diffraction
* Speed remains the same. Diffraction occurs when a wave encounters an obstacle or opening comparable to its wavelength. The wave spreads out as it passes through the opening or around the obstacle. This spreading doesn't change the wave's speed; it only alters its direction and shape.
Key Points:
* Speed is primarily determined by the medium: The speed of a wave is fundamentally determined by the properties of the medium it travels through (like density, elasticity, etc.).
* Reflection and diffraction don't change the medium: Therefore, they don't change the wave's speed.
* Refraction involves a change in medium: This results in a change in the wave's speed.
Example:
Imagine a light wave traveling from air into water.
* Reflection: If the light wave hits a mirror at the surface of the water, it bounces back, maintaining the same speed in air.
* Refraction: If the light wave enters the water at an angle, it bends because the speed of light is slower in water than in air.
* Diffraction: If the light wave passes through a narrow slit (comparable to its wavelength) in a barrier, it spreads out after the slit, but its speed remains the same in air.
