Which one of the following has the longest wave length ?

The electromagnetic spectrum is categorized by wavelength and frequency. According to the standard order from longest to shortest wavelength, the sequence is: radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays [t5, t9]. Infrared radiation has wavelengths ranging from approximately 780 nm to 1 mm, which is significantly longer than visible light (400–700 nm) [t2, t7]. Ultraviolet radiation follows with even shorter wavelengths (50–400 nm), and gamma radiation possesses the shortest wavelengths and highest energy in the entire spectrum [t1, t8, t9]. In the context of solar radiation, the Earth receives energy as short-wave radiation (visible and ultraviolet) and emits it back as long-wave radiation, primarily in the form of infrared [c3]. Therefore, among the given options, infrared radiation has the longest wavelength.

Sources

1. [1] https://imagine.gsfc.nasa.gov/science/toolbox/emspectrum1.html
2. [2] Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 21: Horizontal Distribution of Temperature > Insolation > p. 282