Answer:
<h3>The answer is option B</h3>
Explanation:
The frequency of a wave can be found by using the formula

where
c is the velocity
From the question
wavelength = 0.39 m
c = 86 m/s
We have

We have the final answer as
<h3>200 Hz</h3>
Hope this helps you
Answer:
In D: 3J
Explanation:
Potential energy: Ep=mgh where m is the mass, h altitude.
In point A: h=20cm=0.2m
Epa=12=0.2×mg. Thus mg=12/0.2=60N
For point D: hd=5cm=0.05m
Epd=mg×0.05=60×0.05=3J
Answer:
Violet
Explanation:
Wavelength spectrum of visible light for the range of 390nm to 460nm is seen as violet. So the violet colour will be seen and reflected as what the eyes will see
Answer:

Explanation:
In this case we have to work with vectors. Firs of all we have to compute the angles between x axis and the r vector (which points the charges):

the electric field has two components Ex and Ey. By considering the sign of the charges we obtain that:

Hence, by replacing E1 and E2 we obtain:
![\vec{E}=[(68.67N/C)cos(90\°)-(16.52N/C)cos(17.10\°)]\hat{i}+[(68.67N/C)sin(90\°)-(16.52N/C)sin(17.10\°)]\hat{j}\\\\\vec{E}=(-15.78\hat{i}+63.81\hat{j})\frac{N}{C}](https://tex.z-dn.net/?f=%5Cvec%7BE%7D%3D%5B%2868.67N%2FC%29cos%2890%5C%C2%B0%29-%2816.52N%2FC%29cos%2817.10%5C%C2%B0%29%5D%5Chat%7Bi%7D%2B%5B%2868.67N%2FC%29sin%2890%5C%C2%B0%29-%2816.52N%2FC%29sin%2817.10%5C%C2%B0%29%5D%5Chat%7Bj%7D%5C%5C%5C%5C%5Cvec%7BE%7D%3D%28-15.78%5Chat%7Bi%7D%2B63.81%5Chat%7Bj%7D%29%5Cfrac%7BN%7D%7BC%7D)
hope this helps!!