Penguins can also see into the ultraviolet range of the electromagnetic spectrum. Sparrow Retina has 400,000 photoreceptors per square. Brightness is a perceptual response to the physical property of intensity. Else answer it Summary Light is a transverse, electromagnetic wave that can be seen by humans. Like all electromagnetic waves, light can travel through a vacuum.
Light is produced by one of two methods.
The speed of light depends upon the medium through which it travels. The speed of light in a vacuum is a universal constant in all reference frames. The speed of light in a medium is always slower the speed of light in a vacuum. The speed of anything with mass is always less than the speed of light in a vacuum. The amplitude of a light wave is related to its intensity.