Exploring reflection using Pepper's Ghost

Activity for students aged 11-14 that takes about 20 minutes of class time

Introduction

Type: Starter
Time: 20mins
Subjects: Design & Technology
Key words: light; optical illusion; angle; video; holographic effect; reflection; material; image

Overview
This activity is based on one of the simple tricks or hacks from this year’s CHRISTMAS LECTURES. It is based upon the historical theatre trick of ‘Pepper’s Ghost’ which uses angles of reflection to make an object appear to float in mid-air.
In this activity the students are introduced to an example of Pepper’s Ghost. They are asked to discuss how the illusion works and have a go recreating it.

Materials
Projector or interactive white board
Old unscratched clear CD cases
Smartphone or tablet
Black card and objects to photograph

Media Resources
richannel.org/diy-hologram

Clip

Activity

Show students the clip of the DIY Hologram from the Christmas Lectures (5 mins)

Get students to suggest how they think that this experiment works and ask students what factors they think effect how well that this experiment works (5 mins)

Let students have a go with either a tablet or smartphone to recreate the trick using photographs from their phone (5 mins)

Discuss which of the images works best for creating the illusions and what is the optimal angle for creating the illusion. For what purposes could this illusion be used? (5 mins)

Additional notes

Students can either use their own smartphone or teacher can have one smartphone or tablet for everyone to take turns.

Simple well-lit items with a black background work well for this illusion. If you are using a single smartphone and sharing with the group you can take suitable images in advance using the dark card or paper. Otherwise there are many images of candles against black backgrounds on YouTube that work well. You can also encourage students to search for suitable images.

Differentiation
xxx

Extension
Get students to design a rig which would recreate this effect on a larger scale.
Get students to use protractors to measure the angle at which the images is most viewable.
Students design an experiment to test which angle is best.

Curriculum links

UK Science

  • Experimental skills and investigations
    2b make predictions using scientific knowledge and understanding
  • Analysis and evaluation
    3b interpret observations and data, including identifying patterns and using observations, measurements and data to draw conclusions
  • Light waves
    34c the transmission of light through materials: absorption, diffuse scattering and specular reflection at a surface
    34f colours and the different frequencies of light, white light and prisms (qualitative only); differential colour effects in absorption and diffuse reflection

Design & Technology KS3

  • Design
    1b generate, develop, model and communicate their ideas through discussion, annotated sketches, cross-sectional and exploded diagrams, prototypes, pattern pieces and computer-aided design
  • Technical knowledge
    4a understand and use the properties of materials and the performance of structural elements to achieve functioning solutions

Supported by the Institution of Engineering and Technology

Watch the full lectures

View the full CHRISTMAS LECTURES, Sparks will fly: How to hack your home, along with behind the scenes footage and related content on the Ri Channel richannel.org/christmas-lectures