The resistance of a Cadmium-Sulfide cell “photo cell” in the light is most likely to be ________.

The resistance of a Cadmium-Sulfide (CdS) photo cell, commonly known as a light-dependent resistor (LDR), decreases significantly when light is applied. This behavior is due to the properties of cadmium sulfide, where it exhibits photoconductivity. In brighter conditions, more photons can excite electrons into conduction bands, which leads to a lower resistance.

When there is less light, fewer electrons are excited, resulting in higher resistance. Therefore, in light, the characteristic behavior of a CdS cell is to have low resistance, allowing for more current to flow, which is why the correct answer is that the resistance is low when exposed to light. This property is widely exploited in various applications such as light sensors, automatic lighting systems, and exposure meters in photography.