Find the wavelength of the ultrasonic wave emitted by a bat if it has a frequency of 4.0 * 10^4 Hz.
2 answers:
Remark
You have to pick a velocity for an ultra sound wave. I'm going to take the sound velocity to be 331 m/s in air, because I'm assuming that is what is meant: it is the sound a bat would make once he emits the ultrasound to a microphone like device that receives it. The media through which that happens is air.
Givens
v = 331m/s
f = 4 *10^4 hz
Formula
velocity = wavelength * frequency
v = *f
331/(4*10^4) =
0.008275 =
8.275*10^-3 =
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Answer:
The magnitude of the force on the dipole due to the charge Q =
The magnitude of the torque on the dipole =
Explanation:
Given that a point charge Q is held at a distance r from the center of a dipole that consists of two charges ±q, separated by a distance s and the charge Q is located in the plane that bisects the dipole.
The magnitude of the electric field that the dipole exerts at the position where the charge Q is held is given by
<em>where</em>,
k is the Coulomb's constant, having value =
is the electrical permittivity of free space.
Also, r>>s, therefore,
The magnitude of the electric force F on a charge q placed at a point and the magnitude of the electric field E at that point are related as
Therefore, the electric force on the charge Q due to the dipole is given by
According to Newton's third law of motion, the magnitude of the force exerted by the dipole on the charge Q is same as the magnitude of the force exerted by the charge on the dipole.
Thus, the magnitude of the force on the dipole due to the charge Q =
The magnitude of the torque on the dipole is given by
Since the charge Q is placed in the plane that bisects the dipole, therefore, .