• 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:

If you are connected to the web at the moment, click below to see what’s available:

http://www.physics4u.co.uk/

Definition of Dispersion

Dispersion is the separation of white

light into a spectrum by the process of

refraction.

web site: www.ktaggart.co

m

Dispersion with a prism

•Violet is deviated the most

•Red is deviated the least

•Prism showing light dispersion for different colours

- Explore Science

•Prism & Dispersion - Great Barr School

•Dispersion - Crocodile Clip Presentation

web site: www.ktaggart.co

m

The spectrum of white light

The numbers are the wavelengths

of the colours in nanometres

where 1 nanometre = 0.000 000 001m.

Sequential Puzzle on Colour Spectrum order- by KT

The cause of dispersion

•Dispersion occurs because different colours of light travel at slightly different speeds through transparent substances.• In glass, perspex and water red travels quickest, violet slowest.

The rainbow

An example of dispersion caused by

water

Question 1

Choose appropriate words to fill the gaps in the paragraph below:

•____________ occurs when white light is split up into a ____________ by the process of refraction.

•In glass violet light travels more __________ than the other colours and so is deviated the

_________.

•The spectrum consists of red, ________, __________, _________, ________, indigo and

_________.

•A __________ is formed when water causes dispersion.

Question 2

Explain why

a) orange light is deviated less than blue light in a prism,

b) we know that indigo light travels slower than green light through water,

c) there are seven colours in the spectrum list.

Simulations

Prism showing light dispersion for different colours

- Explore Science Prism & Dispersion - Great Barr School Dispersion - Crocodile Clip Presentation

Sequential Puzzle on Colour Spectrum order- by KT  - Microsoft WORD version

Prism - multishape prism and single light ray - no extra reflections - netfirms

Prism - non dispersive reflections and refractions - NTNU

Puzzles

Convection Crossword – by KT

Related Presentaions

Refraction Powerpoint by KTColour Powerpoint by KT