During the process of reflection, the wavelength and frequency of a wave remain unchanged.

When a wave—such as light or sound—encounters a barrier and is reflected, its properties, including wavelength and frequency, are preserved. This preservation occurs because reflection involves a change in the direction of the wave, rather than a change in its speed or other characteristics. The speed of a wave is determined by the medium through which it travels. Since the medium does not change during reflection, the speed remains constant. Given that the wave speed is directly related to its wavelength and frequency by the equation:

$v = \lambda \cdot f$

where $v$ is the speed of the wave, $\lambda$ is the wavelength, and $f$ is the frequency, it follows that both wavelength and frequency also remain constant during reflection.

The wavelength of a wave is defined as the distance between two consecutive points in the wave that are in the same phase, such as two consecutive crests or troughs. Conversely, frequency refers to the number of complete wave cycles that pass a given point in a specific time interval. These properties are intrinsic to the wave and are determined by the wave’s source, not by the events that occur after the wave is generated. Therefore, when a wave is reflected, its wavelength and frequency do not change.

This principle is fundamental to understanding wave behavior and applies to all types of waves, including light, sound, and water waves. For instance, when light reflects off a mirror, the color of the light—determined by its wavelength and frequency—remains unchanged. Similarly, when sound reflects off a wall, the pitch of the sound—also determined by its wavelength and frequency—stays the same.

In summary, while reflection alters the direction of a wave, it does not modify the wave’s wavelength or frequency. These properties are dictated by the wave’s source and the medium through which it travels, neither of which is affected by the reflection process.