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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Dispersion by a prismDispersion by a prism

New Physics for You, pages 206 - 207

• 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 :

Here is a glass prism:

A ray of white light arrives

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.

In fact, the ray is :• (bent through an angle), and

deviated

• dispersed (split up into separate colours)

like this.

What happens now?

R

VscreenRed is deviated most /

least ?Violet is deviated most / least ?

least

most

R

Vscreen

There is a spectrum

on the screen:

Red Orange Yellow Green Blue Indigo Violet

ROY G BIV

What is the real difference between red and violet light ?4

10 000mm

violet

wavelength

red

710 000

mm

• 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:

For more details, see:

New Physics for You, page 206 - 207

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