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by Vishal Bhatt


While conducting these experiments we will see, that coloured pigments and coloured light mix differently.

So one would use different colour pallets when dealing with pigments, painting, for example, versus when dealing with coloured light, in the case of lighting and screens in electronic devices.

    • Scissors have functional sharp edges. Contact may result in injury. Always keep blades away from fingers and body. Handle with care.

    • Terminals of electronic components might break if twisted to much. Ensure good electrical contact while joining terminals together but take care not to twist too much.

  1. The circuit diagram describes how the LEDs will be connected. Note that, the blue and green LEDs will be connected in parallel to the batteries while the red LED is connected in series with a diode.
    • The circuit diagram describes how the LEDs will be connected. Note that, the blue and green LEDs will be connected in parallel to the batteries while the red LED is connected in series with a diode.

    • Start by drawing an equilateral triangle in the centre of the card sheet. The sides of the triangle need to be 3 cm.

    • The three vertices of the triangle are where the LEDs will be positioned. The red LED is packed with the diode for easy identification.

    • Choose one vertex to be the top of the triangle and insert the red LED under it by pushing the LED into the cardboard.

    • Now identify the positive pin (longer) of the red LED behind the card sheet.

    • Now tie the negative pin of the diode to the positive pin of the LED by twisting them together. The negative pin can be identified by the white strip on the diode-body.

    • Now continue to insert the other two LEDs at the remaining vertices.

    • Behind the cardboard, connect the positive pins of both the green and blue LEDs together.

    • Now you should have two positive pins, one from the combined green and blue LEDs and one from the diode for the red LED. Tie these together by twisting them.

    • You should be left with one positive terminal and three negative terminals. Twist the blue and green LED's negative pins together.

    • Strip a bit of the insulation off the two connecting wires on both sides.

    • Connect one wire to the common positive terminal.

    • Make a hole next to the triangle with the scissors and thread the positive wire through it from back to front.

    • Connect the other wire to the negative of the red LED and measure out the length of wire it takes to reach the other negative(s) on the board.

    • Now cut the wire 1 cm after that point.

    • Strip the two ends of the wire you just cut and twist them back together.

    • Connect the combined strands to the negative of the blue and green LEDs.

    • Make a hole and thread the wire similar to the positive lead.

    • Now connect the positive and negative leads to the positive and negative terminals of the battery holder respectively.

    • All three LEDs should immediately illuminate with roughly equal brightness.

    • Cast the light of the LED on a wall to observe the pattern made by the intersecting spot lights.

    • You can also insert an object in between the LEDs and the wall and observe the effects on the shadow it casts.

    • If one or more of the LEDs don't turn on check their polarity and make sure it matches the batteries polarity.

    • If no LEDs come on, check all connections and try flipping the polarity of the main lead wires.

    • Take any 3 light-coloured sketch pens; we have used pink, yellow and blue.

    • Take a filter paper .

    • Draw a circle and fill it in with any of the colours, pink in our case

    • Make another circle with another colour (blue, in our case)

    • Colour in the circle

    • Make a third circle with the third colour (yellow here)

    • Colour it in yellow

    • You should notice that the colours when drawn on top of each other create a darker and darker spot. A few more added in, and you'll get pretty close to black!

    • Filter paper can tear easily, so do not colour in with too much pressure, especially at the intersection of colours.

    • Using darker hues may create a black spot with just 2 colours, so use lighter colours for a better effect

    • We often call white light a mixture of many colours; how come mixing colours here is creating black and not white?

    • What is the difference when we mix different coloured light with each other (e.g. light from red and green LEDs) compared to what we have done here?

    • Do the same experiment with different sets of colours.

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Kailash NR

Member since: 05/02/2017

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