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:

Two thermometers, calibrated in celsius and fahrenheit respectively, are put into a liquid. the reading on the fahrenheit scale is four times the reading on the celsius scale. the temperature of the liquid is:
Answer: Physical
Explanation: There are no changes being done to the salt. Think of it this way, if you dissolve the salt in water then boil the water completely, you will have the same salt you started with.
Break into small particles. The heat causes the rock to break up and form pebbles or sand. Hope that helped. Have a nice day
Answer:
49N
Explanation:
F=ma
We know the mass is 5kg, and since the ball is suspended on one cable, the acceleration is g, 9.8m/s^2
F=5kg*9.8m/s^2
= 49N
Hope this helps!