What stimulus duration was used?

• A. 1 millisecond
• B. 10 milliseconds
• C. 100 microseconds
• D. 1 second

Answer: (A)

Stimulus duration is how long the light is presented. To probe the immediate, transient response of photoreceptors, researchers use a very brief flash that acts like an impulse. A duration of about one millisecond provides a sharp, time-limited stimulus that elicits the initial phototransduction response without inviting strong adaptation or sustained activity.

If the light were held longer, the response would be affected by adaptation and recovery processes, making it harder to measure the pure impulse timing and amplitude. Too-brief flashes (like microseconds) can be unreliable unless the light is extremely intense, and a long duration such as one second would produce a sustained response that doesn’t capture the initial transient dynamics.