The focal length of the lens is 25cm
given:
power,p=4 diopters
what is focal length?
Focal length is the distance between the point of convergence of your lens and the sensor or film recording the image.
what is diopter?
The unit of optical power of lens is called diopter.It is the optical power of the lens.
we know,
p=1/f
where,
p= power
f= focal length
f=1/p
f=1/4
=0.25m
=25cm
Thus,the focal length of the lens is 25cm
learn more about focal length from here: https/brainly.com/question/28203589
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Placing elements into columns, groups, rows and periods that share certain properties. properties such as gas, solid and liquid determine an element physical state at room temperature.
Answer:

Explanation:
We know that the frequency of the nth harmonic is given by
, where
is the fundamental harmonic. Since we have the values of two consecutive frequencies, we can do:

Which for our values means (we do not need the value of <em>n</em>, that is, which harmonics are the frequencies given):

Now we turn to the formula for the vibration frequency of a string (for the fundamental harmonic):

So the tension is:

Which for our values is:

Answer:
energy is conserved
a force sets an object in motion. when the force is multiplied by the time of its application we call the quantity impulse which changes the momentum of that object. what do we call the quantity force x (times) distance, and what quantity can this change?
Answer:
They will come back at the same time.
Explanation:
The angular velocity equation of ω
where ω is the frequency of the movement, dependent on the angle. But since swings are simple pendulums and their angles of 8 and 4 degrees are small, they will come back to their starting points at the same time.
I hope this answer helps.