An electron is moving in a circular orbit in a uniform magnetic field. is the kinetic energy of the electron changing? select the correct answer and explanation. a: no because the force is always perpendicular to the velocity. b: no because the force is always parallel to the velocity. c: yes because the force is always parallel to the velocity. d: yes because the force is always perpendicular to the velocity.

A: No because the force is always perpendicular to the velocity

Explanation:

The magnetic force does not do any work on the electron. In fact, the work done by the magnetic force is given by:

where

F is the magnetic force

d is the displacement of the electron

is the angle between the direction of the force and the direction of motion of the electron

The magnetic force, however, is always perpendicular to the velocity (and so the direction) of the charged particle: this means that , so and the work done is zero.

According to the work-energy theorem, the change in kinetic energy of the electron is equal to the work done on it:

and so, since the work done is zero, the kinetic energy does not change.

scattering of light by tiny particles in air to produce the colors we see on sky, is dependent on the following factors:

(i) wavelength of light

(ii) size of the scattering particle  

(iii) distance traveled by light through the atmosphere.

according to rayleigh's law of scattering, the amount of scattering is inversely proportional to the fourth power of its wavelength. shorter the wavelength, greater is its scattering. hence violet/blue light is scattered more than red.

sun's light is a composite light ( visible light) with wavelengths in the range 400 nm (violet) to 700 nm (red). as sunlight passes through our atmosphere, the molecules of air scatter light according to their wavelengths. during sunrise and sunset, the sun's position is below the horizon. hence light from the sun travels a greater distance in the atmosphere when compared to its position a noon.

as sunlight enters the earth's atmosphere, blue light is scattered away and at the end of its journey in the sky, only red and orange wavelengths remain in the beam.

hence at sunrise and sunset, the sky appears reddish orange.

dang that balls went far