Final answer:
Two identical light bulbs produce light at around the same frequency, but without coherence, no interference pattern is observed. Coherence is needed for clear interference, and light from regular bulbs have varying phases and spectrums. Lasers can produce interference patterns due to their coherent properties.
Step-by-step explanation:
The question revolves around the concept of light frequency, coherence, and interference. Two identical light bulbs generally produce light of approximately the same frequency, but these light sources are not coherent, meaning their phases are not constant with respect to each other.
Without coherence, an interference pattern will not be observed. Regular light bulbs emit a broad spectrum of frequencies with varying phases, which means their light waves are not aligned in a way that would allow for clear interference patterns as with lasers.
Coherence is crucial for interference patterns, as demonstrated in Young's double-slit experiment using a single light source split into two pathways. In the case of household lighting, factors like the flickering frequency of light bulbs, which is higher than the human eye can detect, prevents us from seeing the flickering effect.
When a light wave enters a different medium, its speed changes but the frequency remains the same, resulting in a change in wavelength.
Using two lasers, which are coherent light sources, will generally yield observable interference patterns, as the waves they emit maintain a constant phase relationship.