For this case we have by definition:
v = λf
We observe that we have a linear relationship, where λ is the constant of proportionality.
We have then:
- <em>v: speed of propagation of the wave
</em>
- <em>λ: wavelength
</em>
- <em>f: frequency
</em>
Answer:
The variable that is directly proportional to the frequency is λ, the wavelength.
Answer : The velocity of an electron is, 
Explanation :
According to de-Broglie, the expression for wavelength is,

and,

where,
p = momentum, m = mass, v = velocity
So, the formula will be:
.............(1)
where,
h = Planck's constant = 
= wavelength = 
m = mass of electron = 
v = velocity of electron = ?
Now put all the given values in formula 1, we get:


Thus, the velocity of an electron is, 
Answer:
The magnitude of the Force is
and the direction is South
Explanation:
From the question we are told that
The magnetic field point due west and since East point toward the positive x -axis
then this magnetic field would be mathematically represented as

Now from the question we are told that the kinetic energy is

Now this kinetic energy can be mathematically represented as

Where m is the mass of proton which has a general value of

Now making the subject of the formula

Substituting values we have


Now from the question we are told that proton is moving upward which is in the positive z direction so the velocity of the proton would be in the positive
So the velocity would be

Now the magnetic Force can be mathematically represented as

Where q is the charge on the proton which has a general value of 
Now substituting the value


Now according to Fleming's left hand rule the direction of the magnetic force is south toward the negative Y - direction 
So the force can be denoted as

Answer:

Explanation:
As we know that the rate of heat transfer due to temperature difference is given by the formula

here we know that

A = 4 m x 7 m
thickness = 30 cm
temperature difference is given as

now we have


Answer:
Ptolemy proposed a model, he reference system is centered on the Earth
Copernicus, proposed a deferent system, this system is centered on the Sun, where it is at the origin of the system
Explanation:
Thousands of years ago, Ptolemy proposed a model to explain the movement of the planets and stars in the sky, in this model the reference system is centered on the Earth, so each body is orbiting in different spheres around the Earth as its center, this system had very complicated calculations and curves to be able to explain the orbits of the planets.
More recently Copernicus, proposed a deferent system, this system is centered on the Sun, where it is at the origin of the system, in this system the movement of the planets are ellipses, which is a much simpler explanation and has been widely accepted, in current systems the reference system is fixed in the bodies more massive, since this simplifies the explanation of the movements.