Final answer:
Microwave ovens and refrigerators are two common sources of interference for a Wireless LAN (WLAN) because they can cause disruptions and signal obstruction in the frequencies used by wireless networks.
Step-by-step explanation:
Two common sources of interference with a Wireless LAN (WLAN) are microwave ovens and refrigerators. Microwave ovens can cause interference because they operate at a frequency of 2.45 GHz, which is very close to the 2.4 GHz band used by many wireless devices including WiFi. This can cause a form of electromagnetic interference in the same frequency range as WiFi, leading to potential disruptions in network performance. Refrigerators or other large metal appliances might not emit interfering signals like microwave ovens, but they can cause signal reflection or absorption due to their large metal structures, potentially obstructing the path of the WiFi signal.
By contrast, DVD players and incandescent light bulbs do not typically operate in the frequency bands used by WLAN and thus are not common sources of wireless interference. Yet, all electronic devices emit some level of electromagnetic radiation, so in very sensitive environments, even these devices might contribute to the overall electromagnetic noise, although it is usually negligible.