The smallest wavelength of light is approximately 10^-18 meters, which corresponds to gamma rays.
Yes, light can have longer wavelengths than what we can see. In fact, infrared and radio waves have longer wavelengths than visible light.
The longest wavelength of light is approximately 10^6 meters, which corresponds to radio waves.
The wavelength of light is measured using a device called a spectrometer, which splits light into its component wavelengths and measures them.
Shorter wavelengths of light have more energy because they have a higher frequency. This means that the waves are closer together and can carry more energy per unit of time.