I added individual steps for clarity. Note that g must be positive if the solution is to be real.

Let me know if you have any questions.
The minimum speed of the particle is the Speed of light in glass is c/μ=2×108m/s.
<h3>Why is the refractive index important?</h3>
The higher the refractive index the slower the light travels, which causes a correspondingly increased change in the direction of the light within the material. What this means for lenses is that a higher refractive index material can bend the light more and allow the profile of the lens to be lower.
Refractive index values are usually determined at standard temperature. A higher temperature means the liquid becomes less dense and less viscous, causing light to travel faster in the medium.
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Answer:

Explanation:
Light rays coming from moon is blocked by the pencil
so as per figure we know that angle subtended by pencil and angle subtended by moon must be same
so we have

so we have

so we have

A watering can is used to hold a water that we will use to water the plants. The water has both mass and volume. Two watering cans are most often different by the volume they contain.
Many various units for volume are used but most often used unit is liter. In a metric system basic units are those such as meter, kilogram and liter while in imperial system units used are those such as foote, inch, pound and gallon.
Unit for volume in metric system is cubic meter. It is equal to a volume of a cube whose all sides measure 1m. This is equal to 1000L. For watering cans that contain several liters units used is decimeter cubed. 1dm^3 = 1L