Answer and Explanation:
Parallax method is used for finding the distance of objects in space there are two types of parallax method that is stellar parallax and trigonometric parallax.The disadvantage of using parallax method is that it can can not reach so far in the Galaxy due to this reason parallax method is generally not used for measuring distance in galaxy.
The anwser is a even bigger wave is coming
Efficiency or 
is calculated by formula: 
where 
also efficiency has no unit.
Now put in the data and calculate the efficiency.
The efficiency of the machine is 0.8
If you want to get percentage just multiply by 100 and you get 80%
Hope this helps.
r3t40
Answer:
Explanation: Light travels at approximately 300,000 kilometers per second in a vacuum, which has a refractive index of 1.0, but it slows down to 225,000 kilometers per second in water (refractive index of 1.3; see Figure 2) and 200,000 kilometers per second in glass (refractive index of 1.5).
