Which retinal system is more sensitive to wavelengths longer than 650 nm?

Which retinal system is more sensitive to wavelengths longer than 650 nm?

• A. Scotopic
• B. Photopic
• C. Purkinje shift
• D. Photochromatic interval

Answer: (B)

The retina uses two main systems for vision: rods for low-light (scotopic) and cones for bright conditions (photopic). Their color sensitivity differs. Rods peak in the blue-green part of the spectrum and fade as wavelengths lengthen into red, so they’re not very responsive to wavelengths longer than about 650 nm. Cones, especially the long-wavelength–sensitive ones, respond to longer wavelengths and carry vision under photopic (bright) conditions, extending sensitivity into the red region beyond 650 nm. That makes the photopic system better suited for detecting light in the >650 nm range. The Purkinje shift describes a different effect related to how brightness perception changes with illumination, where low-light vision relies more on short-wavelength sensitivity, reinforcing that long-wavelength sensitivity comes from photopic (cone) vision. The term about photochromatic interval isn’t a standard retinal concept.

The retina uses two main systems for vision: rods for low-light (scotopic) and cones for bright conditions (photopic). Their color sensitivity differs. Rods peak in the blue-green part of the spectrum and fade as wavelengths lengthen into red, so they’re not very responsive to wavelengths longer than about 650 nm. Cones, especially the long-wavelength–sensitive ones, respond to longer wavelengths and carry vision under photopic (bright) conditions, extending sensitivity into the red region beyond 650 nm. That makes the photopic system better suited for detecting light in the >650 nm range. The Purkinje shift describes a different effect related to how brightness perception changes with illumination, where low-light vision relies more on short-wavelength sensitivity, reinforcing that long-wavelength sensitivity comes from photopic (cone) vision. The term about photochromatic interval isn’t a standard retinal concept.