Which portion of the electromagnetic spectrum is used in a television?
a) infrared waves
b) x-rays
c) radio waves
d) gamma waves

Radio waves are a type of electromagnetic radiation with wavelengths between 10 m to 10,000 m. In the electromagnetic spectrum this wavelength is longer than infrared light and therefore, it goes beyond the visible spectrum.  

This type of electromagnetic waves is very well reflected in the ionosphere, the layer of the atmosphere through which they travel directly or using repeaters.  

In addition, they are very useful to transport information, being important in telecommunications. They are used not only for conventional radio transmissions but also in mobile telephony and TV.  

It should be noted that since radio signals have large wavelengths, they can be diffracted around certain obstacles, such as hills and mountain ranges, preventing the signal from reaching its destination.  

Therefore, the correct option is C.

second mirror gathers light from a faraway object and reflects it to another mirror. - a.

spectral lines lyman is one set