Answer:
It's an Angle of incidence that provides a 90° angle but is also refracted at the same time. it's used to find the water-air boundary (which is 48.6 degrees). in addition, its an angle of incidence value. 
 
        
             
        
        
        
Answer:
4.44s
Explanation:
A 34-kg child on an 18-kg swing set swings back and forth through small angles. If the length of the very light supporting cables for the swing is 4.9 m, how long does it take for each complete back-and-forth swing? Assume that the child and swing set are very small compared to the length of the cables
since the mass of the child and that of the swing is negligible, the masses wont be involved in the calculation
T=2π√L/g
g=acceleration due to gravity which is 9.81m/s2
the length of the supporting cable is 4.9m
T the period
period is the time required to make a complete oscillation
T=2*π√4.9/9.81
T=2*π*0.706
T=4.44s
 4.44s
 
        
             
        
        
        
239.583 days is the answer
        
             
        
        
        
I believe the correct answer from the choices listed above is option C. A group of students is asking people whether they use plastic bags. By doing such, the students are <span>collecting data. They are collecting data of how many people uses plastic bags. Hope this answers the question.</span>
        
                    
             
        
        
        
Mass/density= volume so it will be 360/0.9 which equals to 400 and if you want to find mass you just need to multiple volume•density