Answer:
Explanation:The main purpose of astronomical telescope is to make objects from outer space appear as bright, contrasty and large as possible. That defines its three main function: light gathering, resolution and magnification. These are the measure of its efficiency.
Answer:
The index of refraction of the liquid is 1.35.
Explanation:
It is given that,
Critical angle for a certain air-liquid surface, 
Let n₁ is the refractive index of liquid and n₂ is the refractive index of air, n₂ =1
Using Snell's law for air liquid interface as :




So, the index of refraction of the liquid is 1.35. Hence, this is the required solution.
Work is defined as force*displacement so total d=8.5m and force will be 2kg*g which is roughly 20N of force so W = 20N*8.5m=170J
For part b the gravitational energy is m*g*h so gravitational energy = 200J since 2kg*10 m/s^2 *10m so the change since the work is 170 j means total change is 170J and 30J is left