American Board of Ophthalmology (ABO) Practice Exam

Which color of light has the longest wavelength?

1. Blue

2. Green

3. Red

4. Violet

The correct answer is: Red

The color of light that has the longest wavelength is red. In the visible spectrum of light, wavelengths range from approximately 380 nanometers (violet) to about 750 nanometers (red). Red light, being at the longer end of this spectrum, has wavelengths typically ranging from 620 to 750 nanometers. This longer wavelength is why red light is often associated with lower energy when compared to shorter wavelengths such as blue or violet light. Understanding the characteristics of the visible light spectrum is essential in fields like ophthalmology and optics, as it affects how various wavelengths are absorbed and perceived by the human eye. Red light is also used in various applications and technologies that take advantage of its wavelength properties, such as in lasers and infrared devices. The relevance of wavelength extends beyond perception and includes phenomena such as color mixing and light interference.