EM waves; max value of electric field

In summary, the conversation is about finding the maximum value of the electric field at a distance of 2.5m from a 100W light bulb. The formula E_o = [squ]2S/e_oc is used, but it is incorrect as S, the poynting vector, is not the power of the bulb. Instead, the correct equation is P = S(4[pi]r^2), where r is the distance.
  • #1
Dx
Hello,
What is the max value of the eletric field at a distance 2.5m from 100W light bulb?

I have the formula E_o = [squ]2S/e_oc. This is what i have so far...
E_o = [squ]2(100W)/(8.85x10^-12C^2/Nm^2)(3x10^8m/s) = 274V/m.

My calculations are not right can someone help me with solving for this, please?

Thanks!
Dx :wink:
 
Last edited by a moderator:
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  • #2
Originally posted by Dx
Hello,
What is the max value of the eletric field at a distance 2.5m from 100W light bulb?

I have the formula E_o = [squ]2S/e_oc. This is what i have so far...
E_o = [squ]2(100W)/(8.85x10^-12C^2/Nm^2)(3x10^8m/s) = 274V/m.

My calculations are not right can someone help me with solving for this, please?

Thanks!
Dx :wink:

Wrong equation Dx.
S, the poynting vector, is not the power of the bulb. Rather, Power, P = S(4[pi]r^2). From this you can derive an eqn. which includes r.

Creator
 
Last edited:
  • #3


Hello Dx,

The formula you have used is correct, but you need to make a few adjustments to get the correct answer. First, the power of the light bulb should be converted to watts, which is the unit used in the formula. So, 100W should be written as 100,000,000W. Next, the value of the electric constant should be written in scientific notation as 8.85x10^-12 C^2/Nm^2. Finally, the speed of light should be written as 3x10^8 m/s. With these changes, the calculation becomes:

E_o = [squ]2(100,000,000W)/(8.85x10^-12C^2/Nm^2)(3x10^8m/s) = 3.8x10^7 V/m.

I hope this helps! Let me know if you have any further questions.

 

1. What is an EM wave?

An EM wave, short for electromagnetic wave, is a type of wave that consists of oscillating electric and magnetic fields. They can travel through space and do not require a medium to propagate.

2. What is the maximum value of electric field in an EM wave?

The maximum value of electric field in an EM wave is dependent on the amplitude of the wave. It can vary widely depending on the source and frequency of the EM wave. However, in a vacuum, the maximum value of electric field is approximately 3.335 x 10^11 volts per meter.

3. How are EM waves generated?

EM waves are generated by accelerating electric charges. This can occur naturally through processes such as lightning, or artificially through devices such as antennas or lasers.

4. What is the relationship between the electric and magnetic fields in an EM wave?

The electric and magnetic fields in an EM wave are perpendicular to each other and oscillate in phase. This means that when the electric field is at its maximum value, the magnetic field is also at its maximum value, and vice versa.

5. How do EM waves interact with matter?

EM waves can interact with matter in various ways, depending on the properties of the material and the frequency of the wave. They can be absorbed, reflected, or transmitted through a material. The amount of interaction also depends on the intensity of the EM wave.

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