**Core Concept**
A Wood's lamp is a diagnostic tool used in dermatology to visualize various skin conditions by emitting ultraviolet (UV) light. The specific wavelength of UV light emitted by a Wood's lamp is crucial for its diagnostic capabilities.

**Why the Correct Answer is Right**
The correct wavelength of a Wood's lamp is 365 nanometers (nm), which falls within the UVB spectrum. This wavelength is effective in highlighting certain skin conditions such as vitiligo, albinism, and fungal infections like pityriasis versicolor. The UVB light emitted by the Wood's lamp interacts with the skin's chromophores, causing the fluorescence that aids in diagnosis.

**Why Each Wrong Option is Incorrect**
**Option A:** 254 nm - This wavelength is in the UVC range and is not typically used in a Wood's lamp due to its potential for causing DNA damage and skin burns.
**Option B:** 405 nm - This wavelength is in the violet-blue spectrum and is not effective for highlighting skin conditions.
**Option C:** 510 nm - This wavelength is in the green-yellow spectrum and is not typically used in a Wood's lamp.

**Clinical Pearl / High-Yield Fact**
A Wood's lamp is a valuable diagnostic tool in dermatology, but it should be used with caution and under proper guidance to avoid skin damage.

**Correct Answer: C. 365 nm**