Answer:
v= 1.71 m/s
Explanation:
Given that
Distance between two successive crests = 4.0 m
  λ = 4 m
T= 7 sec
T is the time between 3 waves.
3 waves = 7 sec
1 wave = 7 /3 sec
So t= 7/3 s
We know that frequency f
f= 1/t= 3/7 Hz
Lets take speed of the wave is v
v= f λ
f=frequency
λ=wavelength
v= 3/7 x 4 = 12 /7
v= 1.71 m/s
 
        
             
        
        
        
By definition, power is the amount of energy consumed (or produced) in a second. (or more precisely, it is the rate of change in energy).
so anything which uses energy in a known time period can be labeled with a power rating. 
an example for power could be a nuclear plant; traditional nuclear plants produce somewhat close to 1 giga watts (which means 1 giga joules in a second)
        
             
        
        
        
Shale, sandstone, and limestone are the most commoc types of sedimentary rocks. They are formed by the most common mineral that is found on or near the surface of the Earth
        
             
        
        
        
Glass has a <u>grater </u>index of refraction than air. The glass's and air's indexes of refraction will be 1.5 and 1, respectively.
<h3>What is an index of refraction?</h3>
The refractive index of a substance is a dimensionless quantity that specifies how quickly light passes through it in optics.
The index of refraction of the glass and air will be 1.5 and 1 respectively.
Hence,glass has a <u>grater </u>index of refraction than air.
To learn more about the index of refraction, refer to the link;
brainly.com/question/23750645
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