Consider a monochromatic electromagnetic plane wave propagating in the x direction. At a particular point in space, the magnitude of the electric field has an instantaneous value of 941 V/m in the positive y-direction. What is the instantaneous magnitude of the Poynting vector at the same point and time? The speed of light is 2.99792 x 108 m/s, the permittivity of free space is 8.85419 x 10-12 C2/N/m2 and the permeability of free space is 47 x 10-7 T N/A. What is the direction of the instantaneous magnetic field?
1. B = - 2.
2. B = +î.
3. B = +j.
4. B = - j.
5. B = +k.
6. B = -k.
7. The magnetic field vector does not have an instantaneous direction.
What is the direction of the instantaneous Poynting vector?
1. Ŝ= -î.
2. Ŝ= -k
3. The Poynting vector does not have an instantaneous direction.
4. Ŝ = tî.
5. Ŝ = +Î.
6. Ŝ= -Î.
7. Ŝ= +ê.

a)   S = 2.35 10³   J/m²2 ,  

b)and the tape recorder must be in the positive Z-axis direction.

the answer is 5

c) the direction of the positive x axis

Explanation:

a) The Poynting vector or intensity of an electromagnetic wave is

          S = 1 /μ₀ E x B

if we use that the fields are in phase

          B = E / c

we substitute

         S = E² /μ₀ c

let's calculate

        s = 941 2 / (4π 10⁻⁷  3 10⁸)

        S = 2.35 10³   J/m²2

b) the two fields are perpendicular to each other and in the direction of propagation of the radiation

In this case, the electro field is in the y direction and the wave propagates in the ax direction, so the magnetic cap must be in the y-axis direction, and the tape recorder must be in the positive Z-axis direction.

the answer is 5

C) The poynting electrode has the direction of the electric field, by which or which should be in the direction of the positive x axis

co2reflects heat radiation back to earth buning coal and oil emits co2 globe warms

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.