<span>Cell membranes are selectively permeable because it allows some things to enter or leave the cell while keeping other things outside or inside the cell.</span>
Σ/ε
σ = F/A
ε = ΔL/L
F = force
A = area
L = lenght
ΔL = |old lenght - new lenght|
Answer:
In Newton's 1st Law, a stationary body or that moving with a uniform motion, will only change its state if acted upon by other external forces.This restance to change in position/motion is called inertia. In his second law, when a body is acted upon by a force, the force will be equal to the product of mass and acceleration of the body.i.e. Force= m.a. In the third law, it explains that a body will exert an equal and opposite force when intracting with another body.Here, every action force experiences an equal and opposite reaction force, where the momentum of the bodies will be conserved.
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:
