Phototransistors are sensitive to which type of light?

Phototransistors are semiconductor devices that are designed to detect light and convert it into an electrical signal. They are particularly sensitive to a specific range of light wavelengths, which allows them to effectively function in various applications, such as light detection and optical interfacing.

The correct answer, which is invisible light, encompasses regions of the spectrum not visible to the human eye. Phototransistors are often designed to be sensitive to infrared light, which falls into the category of invisible light. This ability is commonly leveraged in remote control devices, optical communication systems, and motion detection systems.

Understanding the specificity of phototransistor sensitivity is crucial in selecting the right component for electronic circuits and applications. While phototransistors can also respond to visible and ultraviolet light, their typical and most effective use case operates within the invisible spectrum, particularly in the infrared range.