Why do the cabin crew dim the lights for take off and landing?
A look at the reasons that the lights are turned down for certain stages of flight
Why turn down the lights on the aircraft?
It’s probably not the answer you want to hear if you’re a nervous flyer, but the cabin crew turn down the lights for take off and landing (which are the most critical phases of flight) for your eyes to adjust to the darkness, incase of an emergency occurring which requires you to disembark the aircraft quickly. If your eyes are adjusted to the dark, you will be able to find the emergency exit lights and therefore exits easily should the need arise.
You will have the option to use an overhead light which will give you enough light to keep reading or completing a crossword, but these lights are of less intensity, so your eyes should already be adjusted.
This isn’t the same reason they dim the lights in the cruise (at high altitude enroute) – this is to let you sleep!