Answer:
minimum frequency = 170 Hz 
Explanation:
given data 
One path long = 20 m 
second path long = 21 m 
speed of sound = 340 m/s
solution
we get here destructive phase that is path difference of minimum  
 
here  λ is the wavelength of the wave 
so path difference will be 
21 - 20 =  
  
λ = 2 m 
and 
velocity that is express as
velocity = frequency × wavelength    .............1
frequency  =  
  
minimum frequency = 170 Hz 
 
        
             
        
        
        
Since U=0, 
h=1/2gt^2 (h= ut+1/2gt^2, U=0)
h=1/2*10*4*4
h=80m
        
             
        
        
        
Answer:
C
Explanation:
A and B are not true and D is a disadvantage
 
        
             
        
        
        
The element is iridium and it has 77 electrons 
 
        
             
        
        
        
Answer:
The values is  
The  direction is out of the plane 
Explanation:
From the question we are told that 
   The  magnitude of the electric field is  
   
The  magnitude of the magnetic field is mathematically represented as 
        
 where c is the speed of light with value 
       
      
Given that the direction off the electromagnetic wave( c ) is  northward(y-plane ) and  the electric field(E) is eastward(x-plane ) then the magnetic field will be acting in the out of the page  (z-plane  )