Option 1: Radio waves have the longest wavelength among the options provided. They have the lowest frequency and are often used for communication purposes, such as broadcasting radio and television signals.

Option 2: Visible light consists of various colors that we can see with our eyes. It has a wider range of wavelengths compared to radio waves, but it is still longer than both infrared and ultraviolet radiation.

Option 3: Infrared radiation has a shorter wavelength compared to both radio waves and visible light. It is often used for thermal imaging and can be felt as heat.

Option 4: Ultraviolet radiation has the shortest wavelength among the options given. It has higher energy and is frequently associated with the damaging effects of the sun, such as sunburns and skin cancer.

In conclusion, option 4, ultraviolet radiation, has the shortest wavelength among the provided options.