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 & 2011 editions. (or page 216 in GCSE Physics for You, 2001 edition).
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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.
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2. New Physics for You, pages 206 - 207
Dispersion by a prism
New Physics for You, pages

3. Learning Objectives
You should learn :
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.

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

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

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

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

8. There is a spectrum on the screen: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
wavelength
violet
red 7
10 000 mm

10. Learning Outcomes
You should now:
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.

11. For more details, see:
New Physics for You, page
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