Question

A double slit is positioned in front of an incandescent light bulb. Will an interference pattern be produced?

Short answer

Answer: No, a double slit placed in front of an incandescent light bulb cannot produce an interference pattern because the light emitted by the bulb is incoherent and does not maintain constant phase differences over time.

Step-by-step solution

Understand the concept of interference pattern

To produce an interference pattern, light from the two slits should have coherent sources, meaning they maintain constant phase differences over time. Interference patterns are formed when waves from different sources are superimposed on each other. If the waves add constructively (peaks meeting peaks), they form regions of bright light, and if they add destructively (peaks meeting troughs), they form regions of dark light, resulting in an interference pattern.

Light source characteristics

Incandescent light bulbs emit light because the filament (often tungsten) inside gets so hot that it starts to radiate light. The wavelengths of light emitted by an incandescent bulb are continuous and span over a wide range, covering almost the entire visible spectrum. The light produced by an incandescent light bulb is incoherent, meaning it does not maintain constant phase differences over time.

Coherence and interference pattern

Since the light produced by an incandescent light bulb is incoherent, it cannot produce a consistent interference pattern. In coherent light sources, such as lasers, the phase differences are consistent, and constructive and destructive interference can occur, forming a stable interference pattern.

Conclusion

An interference pattern cannot be produced when a double slit is placed in front of an incandescent light bulb because the light emitted by such a bulb is incoherent and does not maintain constant phase differences over time. Therefore, a stable interference pattern will not form in this scenario.

Key concepts

Wave Superposition

When delving into the fascinating world of wave superposition, we explore the behavior of waves as they intersect and overlap. Picture two waves traveling through a medium; when they meet, they don't bounce off each other or become disrupted. Instead, they pass through one another, and at the points where they intersect, the waves combine. This phenomenon, known as wave superposition, leads to either an increase in amplitude (constructive interference) or a decrease to the point of cancellation (destructive interference).

The result is a beautiful dance where crests can meet crests, creating peaks of greater intensity, and troughs may meet peaks, potentially cancelling each other out. This interaction is at the heart of what forms an interference pattern, a hallmark of wave-like behavior observable in various phenomena such as light, sound, and water waves.

Coherent Light Sources

Coherent light sources are pivotal when generating a clear and predictable interference pattern. Coherence refers to the property of waves where the phase difference between the waves is constant; waves are perfectly in sync with each other over time. Lasers are prime examples of coherent light sources, emitting light with a singular wavelength where waves march in unison, maintaining a stable phase relationship.

This creates the opportunity for consistent constructive and destructive interference, the foundations of a stable interference pattern. For applications requiring extreme precision such as holography, optical communications, or interference-based measurements, coherent light sources are indispensable due to their predictable and uniform wavefronts.

Incandescent Light Bulb Properties

Incandescent light bulbs, a common household item, work on the simple principle of heating a filament until it glows. The filament, traditionally made of tungsten, becomes hot enough to emit a broad spectrum of light, covering the visible range and some beyond. This light can be aptly described as 'incoherent' with waves emitted at various times and with various phases, contrasting with the synchronized emissions from coherent sources like lasers.

In an incandescent bulb, electrons move in random motions producing light with various wavelengths and phases. Consequently, even though they light our homes effectively, these bulbs can't create a steady interference pattern when used with devices like double slits which require coherent light to produce such patterns.