Halloween decorations

Safe­ty pre­cau­tions

Warn­ing! Only un­der adult su­per­vi­sion.

Equip­ment

• pro­jec­tor;
• po­lar­iz­er and ship from MEL STEM sets;
• Hal­loween dec­o­ra­tions.

Step-by-step in­struc­tions

This city needs a new hero: pre­pare a bat sten­cil, in­sert the lens into the pro­jec­tor, and dec­o­rate the pro­jec­tor for Hal­loween. Flip the sten­cil up­side down, com­bine it with the dif­fu­sion plate, and fix it to the pro­jec­tor. Point the pro­jec­tor at the wall and shine a bright light on the draw­ing. A bat will ap­pear on the wall!

No storm can scare us: pre­pare pi­rate flags and a sail and fix them to the ship’s mast. As­sem­ble the ship, set it in the wa­ter, and start the en­gine.

Mys­ti­cal kalei­do­scope: cut out a draw­ing from ran­dom­ly-ap­plied strips of Scotch tape. Stick them on a trans­par­ent plate and in­sert the plate into the po­lar­iz­er. Ro­tate the gear of the po­lar­iz­er and ob­serve as the draw­ing shim­mers with all the col­ors of the rain­bow!

Process de­scrip­tion

This city needs a new hero: The light from the flash­light hits the dif­fus­er, uni­form­ly il­lu­mi­nat­ing the im­age cut from the opaque sten­cil. This glow hits the pro­jec­tor lens. The dis­tance from the sten­cil to the screen is such that the im­age is in­vert­ed through the lens, so we flip the sten­cil with the pro­ject­ed im­age in ad­vance!

No storm can scare us: the boat floats on the wa­ter thanks to the por­ous ma­te­ri­al from which its hull is made. The main pro­pel­ler cre­ates a thrust force that sets the boat in mo­tion: while ro­tat­ing, it pass­es air through it­self, push­ing off from it.

Mys­ti­cal kalei­do­scope: Light has an in­trin­sic prop­er­ty called po­lar­iza­tion. A po­lar­iz­ing fil­ter trans­mits light with only one po­lar­iza­tion val­ue, which cor­re­sponds to the ori­en­ta­tion of the fil­ter’s axis. When light pass­es through two po­lar­iz­ers, the amount of trans­mit­ted light de­pends on the rel­a­tive ori­en­ta­tion of the axes of the po­lar­iz­ers: the fur­ther they are from each oth­er, the less light will pass through. Scotch tape changes the po­lar­iza­tion of the light pass­ing through it. This change de­pends on the ori­en­ta­tion of the tape it­self and, more in­ter­est­ing­ly, on the wave­length of the light wave (in oth­er words, the col­or of the light). There­fore, the rays of some col­ors pass through a sys­tem of two po­lar­iz­ers and ad­he­sive tape bet­ter than oth­ers. As a re­sult, each area gets its own col­or, which changes when the po­lar­iz­er is turned.

Ex­cit­ing and safe ex­per­i­ments await you in the MEL Sci­ence sub­scrip­tion!