Experiment of Scattering of Light

1. Aim: To observe the scattering of light in water with and without added particles and understand why the sky appears blue and the sun red at sunset.

2. Requirements: A table lamp (60 or 100 W milky bulb, not LED), thick black paper, sticking tape, a packing needle, a glass beaker (100/200 ml), water, milk or milk powder, a dropper, and a spoon are needed.

3. Procedure

• Cover the lampshade with black paper and secure it with sticking tape.
• Prick a small hole (1-2 mm) in the centre of the paper using a packing needle.
• Fill the beaker with clear water and place it in front of the hole.
• Turn on the lamp and observe the light passing through the water at different angles (front and 90°).
• Add 2-3 drops of milk to the water and stir to make it slightly turbid.
• Observe again. Add more milk if needed to make the water visibly turbid.

4. Observations and Conclusion

• When looking at the beaker from a 90° angle, a blue tinge is visible. This is due to the scattering of blue light.
• From the front view, the light appears red-yellow, as red light scatters less than blue.
• This experiment shows how air molecules scatter blue light from sunlight, making the sky appear blue.
• At sunset, sunlight travels a longer distance through the atmosphere, causing more blue light to scatter away, allowing red-yellow light to reach us, making the sun appear red.

This experiment shows how scattering of light occurs, similar to how sunlight interacts with the atmosphere.