Answer:
utrasonic
Explanation:
these are sounds beyond our hearing capacity range of 20-20kHz
 
        
                    
             
        
        
        
Answer:
At 6 minutes, the soil temperature at a 45° angle of insolation is higher than at 0°.
At 15 minutes, the soil temperature at a 90° angle of insolation is higher than at 45°
Explanation:
 
        
                    
             
        
        
        
Answer:
 = 2.33
Explanation:
.According to snell's law:
n1sin i = n2sin r , 
where n1 is refractive index of the medium in which incident ray is travelling, n2 is the refractive index of the medium in which refracted ray is travelling, 
i is angle of incidence, 
r is angle of refraction.
Given that,
 n1 = 1, 
i = 51 degrees, 
r = 19.5 degrees. , 
n2= ?
So, 
1*sin 51 = n2 sin 19.5  
=> n2 = sin51 / sin19.5
  = 2.33
 
        
             
        
        
        
I’m not sure sorry I really wish I could help