Why are the Doppler effect and diffraction not as commonly observed with light as they are with sound?

Sound waves are a type of mechanical wave that travels through a medium, such as air, water, or solid materials. Unlike light waves, which can travel through a vacuum, sound requires a medium to propagate. The particles within the medium vibrate back and forth, allowing the sound to move from the source to the listener.

These vibrations manifest as variations in pressure, which we interpret as sound when they reach our ears. Because sound relies on the movement of particles, its speed is not only much slower than that of light but also varies depending on the medium it travels through. For instance, sound travels faster in water and even faster in solids than it does in air.

When discussing the Doppler effect in the context of sound waves, it's the changes in pitch we notice as a vehicle with a siren approaches and then moves away from us. The frequency of the waves increases as the source approaches, making the pitch higher, and decreases as it moves away, making the pitch lower. This variation in frequency due to relative motion is often more noticeable in sound than in light due to sound's much slower velocity.

Light waves, by contrast, are electromagnetic and do not require a physical medium to travel. As a result, they can move through the vacuum of space at an incredible speed, approximately 299,792 kilometers per second. The nature of light waves as electromagnetic waves dictates that they have both electric and magnetic field components oscillating perpendicular to each other and to the direction of the wave's travel.

In daily life, we don't typically observe the Doppler effect with light because its speed is so fast that any relative motion between us and a light source doesn't produce a detectable frequency shift, except in extreme cases like those involving astronomical observations or precise satellite measurements.

Light's speed does have interesting effects in other contexts, though. For example, when looking at the stars, we're seeing them not as they are now, but as they were when their light left them, which could be years or even centuries ago. Light also behaves in ways fundamentally different from sound when it encounters obstacles—instead of bending around them to a noticeable extent (as sound does), it often simply reflects off or gets absorbed.

Wave interference patterns are fascinating phenomenons observed when two or more waves overlap and combine. The principle of superposition states that when waves meet, the resultant wave at any point is the sum of the displacements of the individual waves at that point. If the waves have the same frequency and phase, they can constructively interfere, leading to greater amplitude; inversely, if they are out of phase, they can destructively interfere, potentially cancelling each other out completely.

In sound waves, interference can create standing waves in a column of air, like in an organ pipe, resulting in distinct tones. Different points along the wave will either be at a node (where there is minimal movement) or an antinode (where the movement is greatest).

Light waves can also interfere with one another, which is observable in the famous double-slit experiment where light shone through two close slits produces alternating bright and dark fringes on a screen. This interference pattern reveals the wave nature of light and, fascinatingly, can even occur when one photon passes through at a time, implying a single particle of light can interfere with itself. These principles deepen our understanding of wave phenomena and highlight the underlying similarities between various types of waves.