Answer: The frequency of the wave is 0.5 hertz.
Explanation:

= Frequency of the wave
= speed of the light in m/s
= Wavelength of the wave.
Here in question we are given with speed of the infrared light. So, we will replace the value of speed of light(c) from the given value of the speed of the infrared light.
Speed of infrared light = 6 m/s

The frequency of the wave is 0.5 hertz.
Positive because it keeps going ok
These 5 metals are: zinc,copper,tin,bronze,nickel
Fe^2 O^3 + 6HCl --> 2FeCl^3 + 3H^2 O
B, millimeters because paper is really thin therefore it'd require small measurements for units.