What chemical allows us to see black, white and gray colors at night?

What chemical allows us to see black, white and gray colors at night?

• A. Photopsin
• B. Melanin
• C. Opsin
• D. Rhodopsin

Answer: (D)

Night vision relies on rod photoreceptors in the retina, which use rhodopsin to detect light in very dim conditions. Rhodopsin is extremely sensitive and triggers signaling even when only a few photons are present, allowing vision in low light. However, rods do not discriminate colors, so the image seen at night is grayscale—black, white, and gray. In bright light, cones take over and use photopsins to perceive color, which is why color vision fades as it gets darker. The other options aren’t the night-vision pigment: photopsin is associated with cones and color vision, melanin is just a pigment in skin and the eye not involved in phototransduction, and opsin is the protein component of photopigments rather than the pigment itself. Rhodopsin is the pigment specifically responsible for seeing in the dark.

Night vision relies on rod photoreceptors in the retina, which use rhodopsin to detect light in very dim conditions. Rhodopsin is extremely sensitive and triggers signaling even when only a few photons are present, allowing vision in low light. However, rods do not discriminate colors, so the image seen at night is grayscale—black, white, and gray. In bright light, cones take over and use photopsins to perceive color, which is why color vision fades as it gets darker. The other options aren’t the night-vision pigment: photopsin is associated with cones and color vision, melanin is just a pigment in skin and the eye not involved in phototransduction, and opsin is the protein component of photopigments rather than the pigment itself. Rhodopsin is the pigment specifically responsible for seeing in the dark.