A detector whose resistance decreases as light intensity increases is known as what?

A detector whose resistance decreases as light intensity increases is known as what?

• A. LDR (Light Dependent Resistor)
• B. Thermistor
• C. Filament bulb
• D. Diode

Answer: (A)

Light affects a detector’s ability to conduct electricity through a property called photoconductivity. In a light-dependent resistor, darkness leaves the material with few charge carriers, giving it a high resistance. When light shines on it, photons provide energy that frees more charge carriers, so conductivity increases and resistance falls. The stronger the light, the lower the resistance becomes, making it a straightforward light sensor. Other components don’t respond to light in this same way. A thermistor changes resistance with temperature, not light—and it can either rise or fall with heat depending on the type. A filament bulb’s resistance increases as it heats up, which is a thermal effect, not a light-detection behavior. A diode mainly governs current in one direction and isn’t defined by a simple decrease in resistance with light, though some light-sensitive devices exist, the described detector is the light-dependent resistor.

Light affects a detector’s ability to conduct electricity through a property called photoconductivity. In a light-dependent resistor, darkness leaves the material with few charge carriers, giving it a high resistance. When light shines on it, photons provide energy that frees more charge carriers, so conductivity increases and resistance falls. The stronger the light, the lower the resistance becomes, making it a straightforward light sensor.

Other components don’t respond to light in this same way. A thermistor changes resistance with temperature, not light—and it can either rise or fall with heat depending on the type. A filament bulb’s resistance increases as it heats up, which is a thermal effect, not a light-detection behavior. A diode mainly governs current in one direction and isn’t defined by a simple decrease in resistance with light, though some light-sensitive devices exist, the described detector is the light-dependent resistor.