Compounds are elements that are chemically combined, like water for example (it’s both hydrogen and oxygen.)
        
                    
             
        
        
        
Answer:
43.16°
Explanation:
λ = Wavelength = 1.4×10⁻¹⁰ m
θ₁ = 20°
n can be any integer
d = distance between the two slits 
Since for the first bright fringe, n₁ = 1
n₂ = 2 for second order line
The relation between the distance of the slits and the angle through which it is passed is:
dsinθ=nλ
As d and λ are constant

∴ Angle by which the second order line appear is 43.16°
 
        
             
        
        
        
Answer:
What is most widely accepted today is a the giant-impact theory. It proposes that the Moon formed during a collision between the Earth and another small planet, about the size of Mars. The debris from this impact collected in an orbit around Earth to form the Moon.
 
        
             
        
        
        
Answer:
 5.5 × 10-2 hertz
Explanation:
The time taken by a wave crest to travel a distance equal to the length of wave is known as wave period.
= 0.055 per second          (1 cycle per second = 1 Hertz)
Thus, we can conclude that the frequency of the wave is 5.5 X 10^{-2} hertz.
Hopes this helps, love <3