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Q&A Why can someone observe light, even when the light fails to illume that someone?

1 answer  ·  posted 5mo ago by VLDR‭  ·  last activity 5mo ago by Olin Lathrop‭

Question light
#3: Post edited by user avatar VLDR‭ · 2022-04-24T17:34:47Z (5 months ago)
  • I never grokked the optics behind LightHouses and the WW2 poster below work. [LightHouse beams](https://thumbs.dreamstime.com/b/lighthouse-night-beacon-lighting-dark-sky-31776521.jpg) are [narrow and focussed](https://www.google.com/url?sa=i&url=https%3A%2F%2Fwww.pinterest.com%2Fpin%2F464785624045719588%2F&psig=AOvVaw2j4coc8P7Gt-N1oAJ4B6rL&ust=1650907865579000&source=images&cd=vfe&ved=0CA0QjhxqFwoTCPjWo5idrfcCFQAAAAAdAAAAABAJ).
  • Doubtless, the light source can fail to illumine a seafarer or the enemy submarine. But then how can the seafarer or enemy sailors behold your light source?
  • It counters intuition that although a light fails to illumine someone, that observer can still behold the light source! **Can you please correct my intuition?**
  • _**I never studied science after secondary school. Please explain like I am (1)5.**_
  • ![](https://thumbs.dreamstime.com/b/lighthouse-night-beacon-lighting-dark-sky-31776521.jpg)
  • ![](https://i.pinimg.com/originals/c7/7c/d2/c77cd278568a362200d17cfe48db62a4.png)
  • ![](https://townsquare.media/site/959/files/2020/08/TheBeet-Product-Image-Template-2-copy.jpeg?w=630&q=75)
  • ![](https://preview.redd.it/epm131sfnj931.jpg?auto=webp&s=5611303541c2a852364e5c94b3c62d37c23746fc)
  • I never studied science after secondary education. Please explain like I am (1)5.
  • I never grokked the optics behind LightHouses and the WW2 poster below work. [LightHouse beams](https://thumbs.dreamstime.com/b/lighthouse-night-beacon-lighting-dark-sky-31776521.jpg) are [narrow and focussed](https://www.google.com/url?sa=i&url=https%3A%2F%2Fwww.pinterest.com%2Fpin%2F464785624045719588%2F&psig=AOvVaw2j4coc8P7Gt-N1oAJ4B6rL&ust=1650907865579000&source=images&cd=vfe&ved=0CA0QjhxqFwoTCPjWo5idrfcCFQAAAAAdAAAAABAJ).
  • Doubtless, the light source can fail to illumine a seafarer or the enemy submarine. But then how can the seafarer or enemy sailors behold your light source?
  • It counters intuition that although a light fails to illumine someone, that observer can still behold the light source! **Can you please correct my intuition?**
  • _**I never studied science after secondary school. Please explain like I am (1)5.**_
  • ![](https://thumbs.dreamstime.com/b/lighthouse-night-beacon-lighting-dark-sky-31776521.jpg)
  • ![](https://i.pinimg.com/originals/c7/7c/d2/c77cd278568a362200d17cfe48db62a4.png)
  • ![](https://townsquare.media/site/959/files/2020/08/TheBeet-Product-Image-Template-2-copy.jpeg?w=630&q=75)
  • ![](https://preview.redd.it/epm131sfnj931.jpg?auto=webp&s=5611303541c2a852364e5c94b3c62d37c23746fc)
#2: Post edited by user avatar VLDR‭ · 2022-04-24T17:32:21Z (5 months ago)
  • I never grokked the optics behind LightHouses and the WW2 poster below work. Doubtless, the light source can fail to illumine a seafarer or the enemy submarine. But then how can the seafarer or enemy sailors behold your light source?
  • It counters intuition that although a light fails to illumine someone, that observer can still behold the light source! **Can you please correct my intuition?**
  • _**I never studied science after secondary school. Please explain like I am (1)5.**_
  • ![](https://townsquare.media/site/959/files/2020/08/TheBeet-Product-Image-Template-2-copy.jpeg?w=630&q=75)
  • I never studied science after secondary education. Please explain like I am (1)5.
  • I never grokked the optics behind LightHouses and the WW2 poster below work. [LightHouse beams](https://thumbs.dreamstime.com/b/lighthouse-night-beacon-lighting-dark-sky-31776521.jpg) are [narrow and focussed](https://www.google.com/url?sa=i&url=https%3A%2F%2Fwww.pinterest.com%2Fpin%2F464785624045719588%2F&psig=AOvVaw2j4coc8P7Gt-N1oAJ4B6rL&ust=1650907865579000&source=images&cd=vfe&ved=0CA0QjhxqFwoTCPjWo5idrfcCFQAAAAAdAAAAABAJ).
  • Doubtless, the light source can fail to illumine a seafarer or the enemy submarine. But then how can the seafarer or enemy sailors behold your light source?
  • It counters intuition that although a light fails to illumine someone, that observer can still behold the light source! **Can you please correct my intuition?**
  • _**I never studied science after secondary school. Please explain like I am (1)5.**_
  • ![](https://thumbs.dreamstime.com/b/lighthouse-night-beacon-lighting-dark-sky-31776521.jpg)
  • ![](https://i.pinimg.com/originals/c7/7c/d2/c77cd278568a362200d17cfe48db62a4.png)
  • ![](https://townsquare.media/site/959/files/2020/08/TheBeet-Product-Image-Template-2-copy.jpeg?w=630&q=75)
  • ![](https://preview.redd.it/epm131sfnj931.jpg?auto=webp&s=5611303541c2a852364e5c94b3c62d37c23746fc)
  • I never studied science after secondary education. Please explain like I am (1)5.
#1: Initial revision by user avatar VLDR‭ · 2022-04-24T17:26:07Z (5 months ago)
Why can someone observe light, even when the light fails to illume that someone? 
I never grokked the optics behind LightHouses and the WW2 poster below work. Doubtless, the light source can fail to illumine a seafarer or the enemy submarine. But then how can the seafarer or enemy sailors behold your light source?

It counters intuition that although a light fails to illumine someone, that observer can still behold the light source! **Can you please correct my intuition?**

_**I never studied science after secondary school. Please explain like I am (1)5.**_


![](https://townsquare.media/site/959/files/2020/08/TheBeet-Product-Image-Template-2-copy.jpeg?w=630&q=75)

I never studied science after secondary education. Please explain like I am (1)5.