Answer:
Rest and motion are the relative terms because they depend on the observer's frame of reference. So if two different observers are not at rest with respect to each other, then they too get different results when they observe the motion or rest of a body.
Explanation With Example:
Imagine you are sitting inside a moving bus. When you look outside you will observe that you are moving. ... With respect to the roof of bus, you are at rest. Hence it is concluded that rest and motion are relative terms.
1.) Use the formula to solve -
1/f = 1/do + 1/di; Where f = focal length; 1/do + 1/di
1/f = 1/do + di
1/8 = 1/25 + 1/?
.125 = .04 + 1/di
.125 -.04 = 1/di (transferred .04 to the left side of the equation)
.085/1 = 1/di
.085di/.085 = 1/.085 (multiplied both sides by di and divided both sides by .085)
di = 11.76 or 12
2.) Therefore, 12 cm is the distance from the image to the mirror
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:
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