Hello Friends,
Welcome Back,
Its been quite long time since I shared my last post here with you all. So here I am again with you to share my knowledge on one more question that arouse in my mind due to the intense cold wave that is going on in northern part of India.
Yesterday was the most foggy day in my city and I was going to the school in my car with the fog lights of my car on and guiding me the way through the intense fog, and suddenly a question stroked in my mind, that why fog lights are yellow in colour although if we notice in the wavelength series that is VIBGYOR, red colour has the largest wavelength, then why we use yellow light insted of red light in fog lamps.
As per my understanding it is important for fog lights to be one color (rather than white, which is all colors) because the different wavelengths(colors) of visible light scatter off the fog droplets differently. This phenomenon is known as "dispersion," because the different colors of light in an image will separate from each other, causing the image to "disperse." If you illuminate the road with only one wavelength (color) of light, the images of the objects you see will still become somewhat blurry because of the scattering of light by the fog, but at least you won't have extra problems from dispersion. So, if we want to use just one wavelength of light, which wavelength should we use? It turns out that light with short wavelengths scatters more than light with long wavelengths (short to long: violet, indigo, blue, green, yellow, orange, red). So, a long wavelength light will be best. There's another thing to consider, too: our eyes are not equally sensitive to all colors. It turns out that we are most sensitive to yellow and green light. So, our best compromise between sensitivity for our eyes and a long wavelength for least scattering is yellow light.
Now, I don't know what kind of light bulbs are used in fog lights, but another consideration used in street lighting is cost and efficiency. You may have seen some yellow street lighting in some places; this is "low-pressure sodium vapor" lighting. The special thing about this light is that it is almost entirely one (actually two very close together) wavelength of yellow light, and that it gives the most illumination for the amount of electricity.
Red light is used as brake lights in vehicle, therefore we can not use red light as fog lights because then these lights can be misunderstood for break lights and the chance of accidents will increase.
Some persons says that to scatter the light the particles (fog droplets) must be smaller than the wavelength of light, therefore I will also like to tell you all that the size of fog droplets is smaller than the wavelength of yellow light. The average size of fog droplet is 10^-7 m and the wavelength of yellow light is 5.6 x 10^-7 m. So it also supports my theory.
So these are the main reason to use the yellow light in fog lamps.
Good Night friends and sweet dreams......See you in the next post.
Welcome Back,
Its been quite long time since I shared my last post here with you all. So here I am again with you to share my knowledge on one more question that arouse in my mind due to the intense cold wave that is going on in northern part of India.
Yesterday was the most foggy day in my city and I was going to the school in my car with the fog lights of my car on and guiding me the way through the intense fog, and suddenly a question stroked in my mind, that why fog lights are yellow in colour although if we notice in the wavelength series that is VIBGYOR, red colour has the largest wavelength, then why we use yellow light insted of red light in fog lamps.
As per my understanding it is important for fog lights to be one color (rather than white, which is all colors) because the different wavelengths(colors) of visible light scatter off the fog droplets differently. This phenomenon is known as "dispersion," because the different colors of light in an image will separate from each other, causing the image to "disperse." If you illuminate the road with only one wavelength (color) of light, the images of the objects you see will still become somewhat blurry because of the scattering of light by the fog, but at least you won't have extra problems from dispersion. So, if we want to use just one wavelength of light, which wavelength should we use? It turns out that light with short wavelengths scatters more than light with long wavelengths (short to long: violet, indigo, blue, green, yellow, orange, red). So, a long wavelength light will be best. There's another thing to consider, too: our eyes are not equally sensitive to all colors. It turns out that we are most sensitive to yellow and green light. So, our best compromise between sensitivity for our eyes and a long wavelength for least scattering is yellow light.
Now, I don't know what kind of light bulbs are used in fog lights, but another consideration used in street lighting is cost and efficiency. You may have seen some yellow street lighting in some places; this is "low-pressure sodium vapor" lighting. The special thing about this light is that it is almost entirely one (actually two very close together) wavelength of yellow light, and that it gives the most illumination for the amount of electricity.
Red light is used as brake lights in vehicle, therefore we can not use red light as fog lights because then these lights can be misunderstood for break lights and the chance of accidents will increase.
Some persons says that to scatter the light the particles (fog droplets) must be smaller than the wavelength of light, therefore I will also like to tell you all that the size of fog droplets is smaller than the wavelength of yellow light. The average size of fog droplet is 10^-7 m and the wavelength of yellow light is 5.6 x 10^-7 m. So it also supports my theory.
So these are the main reason to use the yellow light in fog lamps.
Good Night friends and sweet dreams......See you in the next post.
nicceeee post.
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