Answer:
Light waves change speed when they pass across the boundary between two substances with a different density , such as air and glass. This causes them to change direction, an effect called refraction . the light speeds up going into a less dense substance, and the ray bends away from the normal.
The global warming is because of the car pollution was the fire in the forest it makes the air one and the warm air grocery Pacific side which makes me glacier it mostly glacier and breaks down two bases and the rising of the water makes the global warming too much so people are trying to use this card and try to use cycles because of global warming .
l hope it helps you bro
THIS IS NOT THE EXACT ANSWER BUT IT MIGHT HELP
The cover slips serves two purposes: (1) it protects the microscope's objective lens from contacting the specimen, and (2) it creates an even thickness (in wet mounts) for viewing.
Answer:
7revolutions
Explanation:
Given parameters:
Initial revolution = 250rpm
Final revolution = 150rpm
Time = 4.2s
Unknown:
Number of revolutions that occur at this time = ?
Solution:
To solve this problem;
let us find the change in revolution = 250rpm - 150rpm = 100rpm
Convert the time to seconds;
60s makes 1 minute
4.2s will make 
= 0.07min
So;
The number of revolutions at this time = 100rpm x 0.07min
= 7revolutions
