Answer: lodestone
An example of a natural magnet is the lodestone, also called magnetite. Other examples are pyrrhotite, ferrite, and columbite.
Classification of Magnets
Lodestones are a common example of natural magnets. Artificial magnets – Artificial magnets can be produced by man-made means and have a stronger magnetic field. They can also be shaped as required. When an artificial magnet is shaped in the form of a bar, it is called a bar magnet.
Explanation:
It is a scaler because it’s only fully describes by a magnitude and a numerical alone
When air is blown into the open pipe,
L = 
where nis any integral number 1,2,3,4 etc. and λ is the wavelength of the oscillation
⇒λ=
Note here that n=1 is for fundamental, n=2 is first harmonic and so on..
⇒ third harmonic will be n=4
Given L=6m, n=4, solving for λ we get:
λ=
=3m
Relationship of frequency(f), velocity of sound (c) and wavelength(λ) is:
c=f.λ Or f= 
⇒f=
≈115 Hz
Newton's law of universal gravitation states that every particle attracts every other particle in the universe with a force which is directly proportional to the product of their masses and inversely proportional to the square of the distance between their centers.
This is mathematically represented as
<u>F= (G X m1 x m2) /r∧2</u>
where F is the force acting between the charged particles
r is the distance between the two charges measured in m
G is the gravitational constant which has a value of <em>6.674×10^-11 Nm^2 kg^-2</em>
m1 and m2 are the masses of the objects measured in Kg
Now if the distance between the is doubled then r becomes 2r. Substituting this in the above formula we get the new Force as
Force (new) = (G X m1 x m2) /(2r)∧2
Thus dividing Force(new)/Force we get
Force(new)/Force = 1/4.
Thus the gravitational force becomes 1/4th of the original value if the distance between the two masses are doubled.
The two correct statement are A and B. Light waves are electromagnetic waves that can travel through a vacuum. Mechanical waves can travel through a vacuum.
<h3>What is an electromagnetic wave?</h3>
EM waves are the electromagnetic radiations are made up of electromagnetic waves created when an electric field collides with a magnetic field.
Electromagnetic waves may alternatively be defined as the combination of oscillating electric and magnetic fields.
Electrically charged particles experiencing acceleration create electromagnetic waves, which can then interact with other charged particles and exert force on them.
The two correct statement is;
1. Light waves are electromagnetic waves that can travel through a vacuum.
2. Mechanical waves can travel through a vacuum.
Hence,two correct statement are A and B.
To learn more about the electromagnetic wave refer to the link;
brainly.com/question/8553652
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