Answer:
Speed is same as that before it entered glass.
Explanation:
Given:
A light ray enters and passes through the glass as shown in the diagram.
We have to analyze its speed.
Speed of light in air is 
and speed of light in glass is 
Whenever a light ray enters a glass block or slab there is bending of light at the interface of the two media.
So speed of light will decrease in glass medium and again it passes to the air.
So
Speed of light in air will again increase or will be equivalent to the earlier speed when it was entering the glass block.
Finally
Speed is same as that before it entered glass as it in the same medium (air).
Answer:at 21.6 min they were separated by 12 km
Explanation:
We can consider the next diagram
B2------15km/h------->Dock
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B1 at 20km/h
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V
So by the time B1 leaves, being B2 traveling at constant 15km/h and getting to the dock one hour later means it was at 15km from the dock, the other boat, B1 is at a distance at a given time, considering constant speed of 20km/h*t going south, where t is in hours, meanwhile from the dock the B2 is at a distance of (15km-15km/h*t), t=0, when it is 8pm.
Then we have a right triangle and the distance from boat B1 to boat B2, can be measured as the square root of (15-15*t)^2 +(20*t)^2. We are looking for a minimum, then we have to find the derivative with respect to t. This is 5*(25*t-9)/(sqrt(25*t^2-18*t+9)), this derivative is zero at t=9/25=0,36 h = 21.6 min, now to be sure it is a minimum we apply the second derivative criteria that states that if the second derivative at the given critical point is positive it means here we have a minimum, and by calculating the second derivative we find it is 720/(25 t^2 - 18 t + 9)^(3/2) that is positive at t=9/25, then we have our answer. And besides replacing the value of t we get the distance is 12 km.
Yes the winds are moving in a straight line
Explanation:
since both the teammates are of the same height, their height won't matter. Because now the basketball won't cover any vertical distance.
We have to calculate its range the horizontal distance covered by it when tossed from one teammate to the other.
range can be calculated by the formula :-
u is the velocity during its take off and 
is the angle at which its thrown
Given that
- u = 8m/ s
- = 40°
calculating range using the above formula
value of sin 80 = 0. 985
Hence,
