Electric field intensity at a distance

AI Thread Summary
The discussion centers on calculating electric field intensity based on the power radiated by a bulb. It is noted that the power at a distance r is given by the formula Power radiated/4πr². A participant initially concludes that halving the power results in halving the intensity, leading to the incorrect assumption that E' equals E/2. The correction emphasizes that intensity is proportional to the square of the electric field, indicating that the relationship is not linear. This highlights the importance of understanding the quadratic relationship between intensity and electric field strength.
Jahnavi
Messages
848
Reaction score
102

Homework Statement


mcq2.jpg


Homework Equations

The Attempt at a Solution



The radiations from the bulb spread radially outwards such that "Power at a distance r" = Power radiated/4πr2 .

If distance is unchanged and power halved then the intensity should also be halved .

From this I get E' = E/2 .

But this is wrong .
 

Attachments

  • mcq2.jpg
    mcq2.jpg
    19.9 KB · Views: 744
Physics news on Phys.org
Jahnavi said:

Homework Statement


View attachment 217104

Homework Equations

The Attempt at a Solution



The radiations from the bulb spread radially outwards such that "Power at a distance r" = Power radiated/4πr2 .

If distance is unchanged and power halved then the intensity should also be halved .

From this I get E' = E/2 .

But this is wrong .
Intensity is propotional to square of elecric field
 
  • Like
Likes Jahnavi
Abhishek kumar said:
Intensity is propotional to square of elecric field

Thanks !
 
Jahnavi said:
Thanks !
Welcome
 
Thread 'Variable mass system : water sprayed into a moving container'

Thread 'Variable mass system : water sprayed into a moving container'

Starting with the mass considerations #m(t)# is mass of water #M_{c}# mass of container and #M(t)# mass of total system $$M(t) = M_{C} + m(t)$$ $$\Rightarrow \frac{dM(t)}{dt} = \frac{dm(t)}{dt}$$ $$P_i = Mv + u \, dm$$ $$P_f = (M + dm)(v + dv)$$ $$\Delta P = M \, dv + (v - u) \, dm$$ $$F = \frac{dP}{dt} = M \frac{dv}{dt} + (v - u) \frac{dm}{dt}$$ $$F = u \frac{dm}{dt} = \rho A u^2$$ from conservation of momentum , the cannon recoils with the same force which it applies. $$\quad \frac{dm}{dt}...
View full post »

Thread 'Struggling to understand the concept of this question (ice cube in water optics question)'

TL;DR Summary: I came across this question from a Sri Lankan A-level textbook. Question - An ice cube with a length of 10 cm is immersed in water at 0 °C. An observer observes the ice cube from the water, and it seems to be 7.75 cm long. If the refractive index of water is 4/3, find the height of the ice cube immersed in the water. I could not understand how the apparent height of the ice cube in the water depends on the height of the ice cube immersed in the water. Does anyone have an...
View full post »

Similar threads

Electric field amplitude question regarding intensity calculations
Replies
4
Views
1K
Intensity and electric field amplitude
Replies
7
Views
2K
Find the electric field of a long line charge at a radial distance
Replies
1
Views
2K
Why is electric field at the center of a charged disk not zero?
Replies
4
Views
3K
Electromagnetic waves radiating away from a transmitting tower
Replies
3
Views
2K
Theory about electric field intensity
Replies
7
Views
2K
What is the relationship between solar radiation intensity and lunar phases?
Replies
11
Views
3K
What causes electric field/ magnetic field?
Replies
3
Views
2K
Intensity of Stars and the Inverse Square Law Problem
Replies
10
Views
3K
Dependence of an electric field on distance
Replies
12
Views
2K

Hot Threads

Recent Insights

Back
Top