What happens to intensity during light interference?

In summary, the conversation discusses the use of COB and SMD technology in LED lighting and the preference for SMD due to its higher lumens per watt. The speaker shares their confusion about the relationship between slit distance and light intensity, and asks for clarification on the impact of multiple light sources on luminous intensity. They also question why COB technology is less efficient than SMD and mention the issue of heat loss. The conversation ends with a brief explanation of how coherent and incoherent light sources affect interference patterns.
  • #1
PiyushA
1
0
Dear Every Smart Person,

I am not a scientist or a physicist by any means, but I have a concept that has been literally driving me crazy all day. No matter how much I read, I can't make sense of it. Here it goes.

I work in the LED Lighting space. In that space, there are two types of LEDs: a "COB" and an "SMD". A COB essentially has numerous LED light sources placed very close together (i.e. several light emitting diodes), whereas an "SMD" is just one light source (a single light emitting diode). The recent trend we are noticing is that people prefer building light products using SMD technology because apparently you get higher lumens per watt compared to using COB technology.

After reading online about light interference and Young's double split experiment, I would have thought that when you have numerous light sources (like multiple LEDs on a COB) pointing in the same direction and placed very close together, you will effectively create higher intensity due to superposition.

After reading the double-slit experiment, I was thinking that maybe if I brought the slits closer together, I can get higher intensity on the screen, but I can't find a single relationship between "slit distance" and "light intensity".

My Questions:
1. Should you have greater luminous intensity because there is multiple light interference happening at the same time causing the amplitude to rise much more quicker, especially since the light sources are placed closer together?

2. Why would the efficiency (lumens per watt) of the light source reduce when you have a COB vs. SMD technology? I would have assumed that since you have overlapping LEDs close together would mean more luminous intensity for the same power output, which would mean a higher lumen per watt product?

3. I heard that because of heat there is light loss using COB light sources over SMDs...but I can solve for the heat problem. And if I did, shouldn't my efficiency from a COB be higher than that from a COB?

Any help is appreciated.
 
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  • #2
If you have separate lamps of any sort, the phase of light from each is not of exactly the same and wanders around, so we can say they are incoherent. This means that when the light falls on a screen we do not see a stationery interference pattern. But with, say, two coherent sources we can say that the fields add, giving peaks of twice the field strength and four times the power flux density. With incoherent sources we say that they add on a power basis, so we have twice the PFD. The average PFD across the screen for both cases is just power addition.
For the case of two sources, the peaks are not dependent on the slit spacing. In the case of Young's slits, however, the two sources are reduced in power as the spacing increases due to diffraction loss caused by the geometry.
 

FAQ: What happens to intensity during light interference?

1. What is light interference?

Light interference is a phenomenon that occurs when two or more light waves overlap and interact with each other. This can result in a change in the intensity and direction of the light waves.

2. How does light interference affect intensity?

The intensity of light waves can either increase or decrease depending on the type of interference. Constructive interference occurs when the peaks of two waves align, resulting in an increase in intensity. Destructive interference occurs when the peaks of one wave align with the troughs of another, resulting in a decrease in intensity.

3. Can light interference be observed in everyday life?

Yes, light interference can be observed in everyday life. Examples include the colors seen in soap bubbles, oil slicks, and thin films like those found on CDs or DVDs. These colorful patterns are a result of light interference.

4. Does the distance between light sources affect interference?

Yes, the distance between light sources can affect interference. In general, the closer the light sources are to each other, the more pronounced the interference pattern will be. This is because the waves are able to interact more closely and create a more distinct interference pattern.

5. How is light interference used in scientific research and technology?

Light interference is used in a variety of ways in scientific research and technology. It is commonly used in optical instruments such as interferometers to make precise measurements of distance, wavelength, and refractive index. It is also used in technologies such as anti-reflective coatings, which reduce unwanted reflections by exploiting the principles of destructive interference.

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