The sensory cell that responds to dim light is referred to as the

Step 1: Analyze the question The question asks which sensory (receptor) cell in the eye responds to dim light. Lens and iris are not sensory cells, so the real contest is between cone and rod.

Step 2: Explain the concept The retina contains two types of photoreceptor cells:

| Feature | Rods | Cones | |---|---|---| | Light sensitivity | Very sensitive, work in dim light | Need bright light | | Vision type | Black and white (no colour) | Colour vision | | Detail (acuity) | Low | High | | Location | Spread over the retina, mostly at the edges | Concentrated at the fovea (yellow spot) | | Pigment | Rhodopsin (visual purple) | Iodopsin |

Step 3: Eliminate the options

• A. Cone: works in bright light and detects colour, so it is not the answer.
• B. Lens: a transparent structure that focuses light onto the retina. It is not a sensory cell.
• C. Rod: contains rhodopsin, which is highly sensitive to low light, so it is correct.
• D. Iris: a muscular ring that controls the size of the pupil and so regulates how much light enters the eye. It is not a sensory cell.

Step 4: Answer The sensory cell that responds to dim light is the rod.

Tip: Think of Rod = Room is dark (dim light), and Cone = Colour. This is why we struggle to see colours at night: only the rods are working.