Astronomers build optical telescopes on tops of mountains because a. there is less air to dim the light. b. the seeing is better. c. CCDs work better with a beautiful mountain view. Astronomers build optical telescopes on tops of mountains because a. there is less air to dim the light. b. the seeing is better. c. CCDs work better with a beautiful mountain view. all choices, a, b and c choice c only choice a only choice b only choices a and b

choices a and b

Explanation:

Telescope can be defined as am optical instrument which is designed to observe the distant objects clear and nearer. It comprises of arrangement of lenses which allow the rays of light to be collected. The collected light is focused and the image so produced is magnified in the form of an image. The telescopes are prepared and manufactured on mountains top as this will help in preventing the distortion of light obtain from the star due to the fluctuation of air mass in the atmosphere. The atmospheric distortion affects the resolution, and affects the vision. The atmospheric pressure is low at the mountain tops so it will help in better observation of the sky.

adding a(n) to an electric circuit would increase the magnetic field around a wire;

b. solenoid

a solenoid is a type of electromagnet whose purpose is to generate a controlled magnetic field.

if the purpose of the solenoid is instead to impede changes in the electric current, a solenoid can be more specifically classified as an inductor rather than an electromagnet.

friction

explanation:

they us to move forward and backwards