Answer:
The intensity of laser 2 is 4 times of the intensity of laser 1.
Explanation:
The intensity in terms of electric field is given by :

E is electric field
It means, 
In this problem, lasers 1 and 2 emit light of the same color, and the electric field in the beam of laser 1 is twice as strong as the e-field of laser 2.
Let E is electric field in the beam of laser 1 and E' is the electric field in the beam of laser 2. So,

We have,
E'=2E
So,

So, the intensity of laser 2 is 4 times of the intensity of laser 1.
So you can have a understanding of what you are doing and figure out your overall goal
Answers is F=7.84 N
Friction force resists the effect of horizontal force and trying to approch to a limiting force.
we have formula for limiting friction force between block and floor
F=Ц N
where N=mg
putting values we get answer.
Answer:

Explanation:
For n-=1 state hydrogen energy level is split into three componets in the presence of external magnetic field. The energies are,
,
,

Here, E is the energy in the absence of electric field.
And
are the highest and the lowest energies.
The difference of these energies

is known as Bohr's magneton.
B=2.5 T,
Therefore,

Now,

Therefore, the energy difference between highest and lowest energy levels in presence of magnetic field is 
Answer:
1.The Sun is located at one of the foci of the planets' elliptical orbits.
2.The path of the planets around the Sun is elliptical in shape.
Explanation:
As per Kepler's law of planet motion we know that all planets revolve around the sun in elliptical path in such a way that position of Sun must be at one of the focii of the path
So all planets are in elliptical path always
Position of sun is always at one of the focus
so correct answer will be
1.The Sun is located at one of the foci of the planets' elliptical orbits.
2.The path of the planets around the Sun is elliptical in shape.