The last one is true.
Lets say that wave 1 has function of W1 = A*sin(w*t) and second one
W2 = A*(w*t - 180)
both waves have same amplitude A and same frequency (w=2*pi*f)
in t=0 first wave has value of 0 and second one has value of 0. Their sum is equal to 0.
As the time starts passing first wave's value will grow while second one will decrease and go negative (because of the shape of sinus function). Both of them are changing their value at same rate because of same frequency and their sum will always be 0. Check the graph.
Answer:
Inverse proportion, greater
Explanation:
The relation between wavelength (λ) and frequency (ν) is given by

Where
speed of light in vacuum.
We can see from this equation that wavelength and frequency are related inversely.
Now,

Where 'E' is energy of electromagnetic radiation and 'h' is Planck's constant.
We can see from this equation that greater frequency (ν) will give greater electromagnetic radiation (E). As they are directly proportional.
Hence,
When decreasing electromagnetic radiation there is a(n) Inverse proportion relationship between wavelength and frequency and the greater the frequency, the greater energy the electromagnetic radiation has
a friction force 10 N less than the applied force, a normal force equal to the gravtiational force
Answer: 0.25 m/s
Explanation: Speed = wavelengt · frequency
v = λf and frequency is 1/period f = 1/T
Then v = λ/T = 5 m / 20 s = 0.25 m/s