**Core Concept**
Rhodopsin is a light-sensitive receptor protein in the retina that plays a crucial role in low-light vision. It is a complex of a protein called opsin and a vitamin A derivative called 11-cis retinal. When light enters the eye, it triggers a conformational change in the 11-cis retinal, which activates the opsin protein and initiates a signaling cascade that ultimately leads to visual perception.

**Why the Correct Answer is Right**
Rhodopsin has a peak sensitivity to light of wavelength 500 nm (green light) due to the specific structure of its 11-cis retinal component. The 11-cis retinal molecule absorbs light most efficiently in the blue-violet end of the visible spectrum, which is why rhodopsin is most sensitive to light with a wavelength around 500 nm. This allows the rod cells in the retina to detect even small amounts of light and transmit signals to the brain for visual perception.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because rhodopsin is not most sensitive to light with a wavelength around 400 nm (violet light), which is actually absorbed by the cone cells in the retina that are sensitive to red light.
**Option B:** This option is incorrect because rhodopsin is not most sensitive to light with a wavelength around 600 nm (red light), which is actually absorbed by the cone cells in the retina that are sensitive to blue light.
**Option D:** This option is incorrect because rhodopsin is not most sensitive to light with a wavelength around 700 nm (infrared light), which is actually absorbed by the skin and is not visible to the human eye.

**Clinical Pearl / High-Yield Fact**
Rhodopsin's peak sensitivity to light is an essential adaptation that allows the human eye to detect even small amounts of light in low-light conditions, making it an essential component of night vision.

**Correct Answer:** C. 500 nm.