True or false: Rods have directional sensitivity.

True or false: Rods have directional sensitivity.

• A. True
• B. Not applicable
• C. Both rods and cones have directional sensitivity
• D. False

Answer: (D)

Rods are built for detecting light intensity in dim conditions, not for sensing where light comes from. Their photopigment absorbs photons across a broad range of angles, giving an overall, isotropic response that reflects how much light is present rather than its direction. In low light, vision relies on summing signals from many rods across a wide retinal area, which emphasizes sensitivity over directional detail. Directional sensitivity would require a photoreceptor to prefer light from a particular angle, and rods don’t have that property. Cones behave similarly in this respect, though they provide high-acuity color vision in bright light. So the statement is false.

Rods are built for detecting light intensity in dim conditions, not for sensing where light comes from. Their photopigment absorbs photons across a broad range of angles, giving an overall, isotropic response that reflects how much light is present rather than its direction. In low light, vision relies on summing signals from many rods across a wide retinal area, which emphasizes sensitivity over directional detail. Directional sensitivity would require a photoreceptor to prefer light from a particular angle, and rods don’t have that property. Cones behave similarly in this respect, though they provide high-acuity color vision in bright light. So the statement is false.