Twenty is the atomic number of potassium.
The answer is A. Polarized in a vertical plane
If positioned correctly, a polarized lenses can block all reflected light from horizontal surface such as road
<h2><u>Q</u><u>u</u><u>e</u><u>s</u><u>t</u><u>i</u><u>o</u><u>n</u>:-</h2>
The speed of a wave is 40 m/s. If the wavelength is 80 centimeters, what is the frequency of the wave ?
<h2><u>A</u><u>n</u><u>s</u><u>w</u><u>e</u><u>r</u>:-</h2>
<h3>Given:-</h3>
Velocity (V) = 40 m/s
Wavelength
= 80 cm = 0.8 m
<h3>To Find:-</h3>
The frequency (F) of the wave.
<h2>Solution:-</h2>
We know,

40 = F × 0.8
F = 
F = 50
<h3>The frequency of the wave is <u>5</u><u>0</u><u> </u><u>H</u><u>z</u>. [Answer]</h3>