The need to quickly move through dark environments.  <span />
        
                    
             
        
        
        
Wind and Waves are the 2 main forms of erosion on coastline cliffs
 
        
             
        
        
        
Answer:
 76.74 Hz
Explanation:
Given:
Wave velocity ( v ) = 330 m / sec
wavelength ( λ ) = 4.3 m
We have to calculate Frequency ( f ): 
We know:
v = λ / t [ f = 1 / t ] 
v = λ f
= > f = v / λ
Putting values here we get:
= > f = 330 / 4.3 Hz
= > f = 3300 / 43 Hz
= > f = 76.74 Hz
Hence, frequency of sound is 76.74 Hz.
 
        
             
        
        
        
A standing wave is the result of a reflection. 
        
                    
             
        
        
        
<span>Objective Lenses: Usually you will find 3 or 4 objective lenses on a microscope. They almost always consist of 4X, 10X, 40X and 100X powers. When coupled with a10X (most common) eyepiece lens, we get total magnifications of 40X (4X times10X), 100X , 400X and 1000X.</span>