Phototransistors are sensitive to which type of light?

Phototransistors are designed to respond to light, but their sensitivity extends beyond what is visible to the human eye. They primarily detect invisible light, which includes both infrared and ultraviolet light, depending on their specific design and materials used in their construction. This characteristic makes them versatile components in various applications, such as light detection and automation systems, where different wavelengths of light are utilized for activation or sensing.

While some phototransistors may have varying sensitivity ranges, the option that encompasses the broader spectrum of light types, including infrared, is the most appropriate. This is crucial for understanding how different light wavelengths interact with electronic components, allowing for specialized applications in technology where the presence of light, even if not visible, needs to be sensed accurately.