• Question: why on some laptops if you press the screen it goes black???

    Asked by lionalmessi to Anil, Blanka, Cees, Emma, Mike on 29 Jun 2012.
    • Photo: Michael Cook

      Michael Cook answered on 29 Jun 2012:


      It depends what type of laptop it is! It’s probably an LED/LCD screen, though – these screens are made up of hundreds of rows of tiny glass boxes, and in each one is some liquid crystal. The liquid is used to change the colour of light being shone through it, so we can see the whole range of colours on our screens (I talked about this in a question about televisions: /niobiumj12-zone/2012/06/27/how-are-the-tvs-made/).

      When you push down on these, all sorts of things can happen – the little glass boxes can be permanently damages (leaving “dead pixels” which are black or white dots that never go away). These are normally caused by the electronics being broken, and permanently setting some boxes on or off, so you only see full white colour or full black colour in those areas.

      Sometimes you don’t permanently damage the screen, and it just looks a bit funny for a while. This is just because things are pushed slightly out of place by the pressure of your finger (the liquid crystal, for instance, is very easy to move around if you push down on a screen). Over time everything slowly goes back to the position it was in originally, and hopefully there’s no permanent damage!

      I have some dead pixels on the screen I’m using to write this answer! I dropped my MacBook once and there are bits of the screen that are always very bright white. I need to replace this laptop!

    • Photo: Emma Trantham

      Emma Trantham answered on 29 Jun 2012:


      I’m glad Mike’s around to answer these techie questions! 🙂

    • Photo: Blanka Sengerova

      Blanka Sengerova answered on 29 Jun 2012:


      Wow, I am learning new things together with you guys by reading the other scientists’ answers.

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