Can you make a ghost appear in your classroom?
Take a piece of glass from a picture frame of any size and find or make a box that the glass will fit into across the diagonal.
Leave the top of the box open and cut out a doorway on the lefthand side of the front of the box.
Using a thick black marker pen draw diagonal lines across the inside bottom of the box. Then draw diagonal lines in the opposite direction to form a check effect. Draw a picture as a backdrop and stick it on the inside of the back of the box.
Place the glass diagonally so it fits between the near left side and the far right side of the box.
Draw around the bottom of the box and cut out a piece of card the same size. Cut along the diagonal to make a triangle of card. Sellotape the card to the top of the piece of glass, so the card can act as a flap.
Attach a tab to the flap so you can make it fall as a lid to either the left or right side of the box. Take a plastic figure about 5cm high and place it in front of the glass on the right. You should not be able to see this figure when you look through the doorway.
Place the box in an area that you can darken, and place a light about 50cm above the top of the box.
Turn the light on. Move the flap of cardboard between the two positions and watch what happens through the doorway. A transparent ghost will appear when the flap covers the lefthand side of the box.
The trick helps your students think about light.
When the flap is over the front of the box to the right side, the light from the lamp does not hit the model, and no ghost is seen.
When the flap is over the other side, the light hits the model.
Most of the light passes through the glass but a small amount is reflected.
Your brain is fooled into thinking that this light is coming from the left hand side of the box and a ghostly reflection is seen through the doorway.