Answer:
He is using a REFLECTING TELESCOPE.
Explanation:
A telescope is an optical instrument that is used by scientists or astronomers to view objects that are very faraway such as objects that are in space. For example: the galaxies, the stars, the moon, the planet e.t.c.
The mode of operation of a telescope is, a telescope makes use of either a lens or mirrors which are curved. This lens or mirrors focus the light rays from the faraway objects and uses them to form an image.
We have two types of telescopes.
a. Refracting Telescope: Another name for a refracting telescope is a refractor. The refracting telescope uses a lens to focus the rays of light and form an image.
b. Reflecting telescope: This is also called a reflector. It is different from the refracting telescope because it makes use of curved mirrors to focus the rays of light and form an image. The images formed by reflecting telescopes are very big and clear. Those images are also free from any form of abberation such as chromatic abberation.
From the above question, Phillip is using an optical device to look at the stars. He knows that it uses mirrors, but cannot remember its name. He is using a REFLECTING TELESCOPE. The reason for my answer is because it is said in the question that the optical device makes use of mirrors and it is only a reflecting telescope that uses mirrors.
