Question

light waves traverse in straight lines until they strike a surface. when light waves strike a surface, three things can happen. the light waves may be absorbed by the surface, bounce off the surface, or pass through the surface. the bouncing of light waves off of an object is reflection. these objects are seen when the reflected light waves strike someones eyes. a mirror is an example of this. refraction is the bending of light, and takes place when light waves travel through two different transparent materials. observing a straw in a glass of water appearing to bend would be described as refraction, or the bending of those energy waves. the range of energy waves that includes all visible and invisible light waves is called the electromagnetic spectrum. waves in the electromagnetic spectrum are arranged by the amount of energy they have. gamma waves are extremely powerful, and have the most energy of all the waves in the electromagnetic spectrum. they are used to fight types of cancer. another type of wave is x - rays. these easily pass through skin, but not bones. ultraviolet waves are also found on the spectrum. humans cant see ultraviolet waves. however, some insects and animals can. why did the author begin the sentence at the end of paragraph 4 with however? select one: to suggest that humans and animals are similar and can both see ultraviolet waves. to signal that the author was switching to a new topic and discussing a new wave. to indicate that there will be a contrast between the previous and the current sentence. to reveal that the electromagnetic spectrum is not visible to anyone.

Explanation:

The word "However" is a transition word often used to show contrast. In the context, it contrasts the fact that humans can't see ultraviolet waves with the fact that some insects and animals can.

Answer:

To indicate that there will be a contrast between the previous and the current sentence.