The jpoc airline passengers guide asks:
Why do they turn the lights off during take off and landing?
"Ladies and Gentlemen, we will be dimming the cabin lights for take off. If you wish to continue reading, please use the reading light above your head."
You have heard that at the start of every commercial flight made in the hours of darkness for as long as you can remember.
Like most passengers, you occasionally wonder why and discuss the matter with your friends. Perhaps, you even asked one of the cabin crew why they do it. Their reply is like the mythical computer support answer: factually correct but no use to you whatsoever. They explain that it is an international civil aviation regulation. But why?
Well, the answer is simple. The cabin lights are dimmed during landing and take off in the hours of darkness so that the passengers' eyes will be used to low levels of light. What good is that? Well, most aircraft accidents occur during landing and take off and if this happens, you can bet that the cabin lights would go out pretty quickly. If they had been set to their normal level before that, everyone's eyes would be used to high light levels and, in the resulting darkness, most people would be able to see very little indeed.
By dimming the lights, they ensure that passengers are better prepared to deal with any emergency that will involve evacuating the aircraft in darkness.
Of course, this is why you will not be told the reason for dimming the lights if you ask a member of the cabin crew. Nobody wants to suggest to their passengers that the aircraft might be about to crash.
Now you are really worried and you want to know if you should actually turn off your reading light for extra safety. My advice is not to worry about that. The intensity of the reading light is a lot lower than that of the cabin lights.
The final question has to be: "Is all this worthwhile?" Is it really a benefit to have your eyes attuned to low light levels? Well, to answer that, you should be aware of the history of aircraft accidents. Consider the class of accidents in which the aircraft is badly damaged and there is a fuel fire but most passengers survive the initial impact. Over the years, experience has shown that it is unlikely that all passengers will be able to leave the aircraft before they are overcome by smoke and fire. Some number of people will die. Even if dimming the lights makes a difference of just a few seconds, it will mean the difference between life and death for some passengers at the back of the queue to exit the aircraft.