Have you ever sat in the front seat of a car at night? Road reflectors, street signs and even road paint all shine bright under car headlights. Make your own ‘road paint’ and see if you can make it shine with glass beads!
You will need
- Black card
- White paint
- Palette or scrap of cardboard to put paint on
- Paintbrush
- Clear glass seed beads
- Glitter (you can buy biodegradable glitter from some makeup stores or online)
- Silver pen
- Torch
What to do
- Start by squeezing out some white paint onto a palette or a scrap of cardboard.
- Paint 4 thick white lines on your black cardboard. Make sure you use lots of paint!
- Sprinkle seed beads on the first line.
- Sprinkle glitter on the second line.
- Wait for the paint to dry.
- Shake off any extra glitter and beads.
- Use the silver pen to colour in the third line.
- Leave the fourth line alone.
- We’ve got 4 lines here, and three of them are shiny or reflective. Which one do you think will work best at night?
- Time to test your lines! Put the cardboard on a table in a dark room. Turn on your torch and shine it at the lines. Which line looks brightest?
- Move the torch close to your eye but keep it pointed at the lines. Which is brightest now?
- For a photographic test, take one photo with the flash on, and one with the flash off. Do you notice any difference between the 2 pictures?
What’s happening?
If you look out the front window of a car at night, you’ll notice many things light up brightly. Signs, reflectors and even the paint on the road can glow brighter than seems possible.
The secret is retroreflection. While a mirror only reflects back at you if you’re standing right in front of it, Retroreflectors are different. A retroreflective object reflects light back the way it came, even when it comes in from an angle. That superpower makes them great for road markings. When you’re in a car at night, the light from the headlights is reflected back to the car, making objects glow brightly.
There are many ways to make something retroreflective. The reflectors in the middle of the road and on bicycle wheels use little mirrors arranged in corner shapes, and bounce light around the corners and back the way it came.
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