The frequency is 
and it is blue light
Explanation:
The relationship between the speed, the frequency and the wavelength of an electromagnetic wave is given by:
where
is the speed of light
f is the frequency of the wave
is its wavelength
In this problem, the wavelength of the wave is
Therefore, its frequency is:
The wavelength of this wave is
And by looking at the table of the wavelengths of the colors, we notice that this corresponds to the blue light, which has a range of wavelength of
[450 - 495] nm
Learn more about waves and electromagnetic waves here:
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<span>Three-fourths of the illuminated side of the moon be visible
from Earth when the moon is at position-B. (choice-B)
Notice the particularly egregious screw-up on the drawing at the
"Third Quarter" position. There, the drawing shows the illuminated
side of the moon AWAY from the sun, and the dark side of the moon
TOWARD the sun. That's about as silly as you can get. </span>
A. Earth is orbiting the sun
By definition, the wavelength of an electromagnetic wave is calculated using the following formula:
Where:
\lambda = wavelength
c = speed of light = 
f = frequency of the wave.
This relation means that the division of the wavelength λ between the frequency f is always equal to the speed of light.
Thus:
the velocity v of this wave must be equal to c.
Finally the correct answer is D. 
If 56.5kJ are needed to raise the temp by 90°C and if the heater is 60% efficient that means that:
60% X y = 56.5kJ
where y is the electrical energy in kJ that the heater will use.
y = 94.2kJ
