For example, H-Cl has a dipole. The electrons spend more of their time near the Cl atom (the red end in the diagram below). A dipole-dipole interaction is the attraction between two polar molecules. When they approach each other, the negative end one molecule attracts the positive end of the other.
Eyes sensitive to light can also be caused by viruses or inflammation, such as those found in sinus infections. If you have a cough, aching jaw, blocked nose, headaches and lethargy then it's best to visit your GP for a diagnosis of a possible sinus infection and simple antibiotic treatment.
The human eye is only sensitive to EM radiation at wavelengths that range roughly between 780 nanometers and 380 nanometers. This small segment is called the visible spectrum or visible light. This is usually what we mean when we speak of light (though, properly speaking, all EM radiation is light). Infrared lies just below red light; ultraviolet exists just above violet light. Both are invisible to humans and other creatures (though some reptiles can see infrared and some insects can see ultraviolet).