1. Teacher’s Notes This sequence of slides is designed to introduce, and explain dispersion by a prism to produce a spectrum, as explained on page 206 in New GCSE Physics for You, 2006 edition. (or page 216 in GCSE Physics for You, 2001 edition). On each slide the key points are revealed step by step, at the click of your mouse (or the press of a key such as the space-bar). Before making the next mouse-click you can ask questions of the class or make statements about what is about to be revealed. This should help students to become clearer about the ideas involved. Naturally it pays to have quick practice-run first. To start the slide-show, press function-key F5 (or right-click->Full Screen) (to return to ‘normal view’ press the key). For more free PowerPoint presentations, visit www.physics4u.co.uk

2. Dispersion by a prism New Physics for You, pages 206 - 207

3. How a light ray is deviated by a prism, How white light is dispersed by a prism, The colours of a white light spectrum, About the wavelengths of different colours. Learning Objectives You should learn :

4. Here is a glass prism: A ray of white light arrives

5. It is (mainly) reflected or refracted ? away from or towards the normal the normal What happens to the ray of light? But different colours are refracted by different angles.

6. In fact, the ray is : (bent through an angle), and devi ated dispersed (split up into separate colours) like this.

7. What happens now? R V screen Red is deviated most / least ? Violet is deviated most / least ? least most

8. R V screen There is a spectrum on the screen: Red Orange Yellow Green Blue Indigo Violet ROY G BIV

9. What is the real difference between red and violet light ? 4 10 000 mm violet wavelength red 7 10 000 mm

10. Understand what happens when white light enters a prism, Distinguish between deviation and dispersion, Know the colours of the spectrum, in order, Understand the connection between colour and wavelength. Learning Outcomes You should now:

11. For more details, see:  New Physics for You, page 206 - 207 For more free PowerPoints, visit  the web-site at www.physics4u.co.uk

12. If you are connected to the web at the moment, click below to see what’s available: http://www.physics4u.co.uk/