1. Frequency: 
The frequency of a light wave is given by:

where
is the speed of light
is the wavelength of the wave
In this problem, we have light with wavelength

Substituting into the equation, we find the frequency:

2. Period: 
The period of a wave is equal to the reciprocal of the frequency:

The frequency of this light wave is
(found in the previous exercise), so the period is:

Answer:
It looks like you have some writing to do ,(-:
Explanation:
Answer:
I think it's C I'm so sorry if I'm wrong.
Explanation:
The value of cos θ in the given figure is 0.98.
<h3>
What is cosine of an angle?</h3>
The cosine of an angle is defined as the sine of the complementary angle.
The complementary angle equals the given angle subtracted from a right angle, 90.
cos θ = sin(90 - θ)
For example, if the angle is 30°, then its complement is 60°
cos 30 = sin(90 - 30)
cos 30 = sin 60
0.866 = 0.866
<h3>Cosine of an angle with respect to sides of a right triangle</h3>
cos θ = adjacent side / hypotenuse side
adjacent side of the given right triangle is calculated as follows;
adj² = 10² - 2²
adj² = 100 - 4
adj² = 96
adj = √96
adj = 9.8
cos θ = 9.8/10
cos θ = 0.98
Thus, the value of cos θ in the given figure is 0.98.
Learn more about cosine of angles here: brainly.com/question/23720007
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From conservation of energy, the height he will reach when he has gravitational potential energy 250J is 0.42 meters approximately
The given weight of Elliot is 600 N
From conservation of energy, the total mechanical energy of Elliot must have been converted to elastic potential energy. Then, the elastic potential energy from the spring was later converted to maximum potential energy P.E of Elliot.
P.E = mgh
where mg = Weight = 600
To find the height Elliot will reach, substitute all necessary parameters into the equation above.
250 = 600h
Make h the subject of the formula
h = 250/600
h = 0.4167 meters
Therefore, the height he will reach when he has gravitational potential energy 250J is 0.42 meters approximately
Learn more about energy here: brainly.com/question/24116470