Dispersion by a prism

1
Teachers Notes This sequence of slides is
designed to introduce, and explain dispersion by
a prism to produce a spectrum, as explained on
pages 210-211 in Physics for You, 5th edition.
(or pages 206-7 in GCSE Physics for You, 2011
edition). Note When you start this PowerPoint
if you see a message about Read-only embedded
fonts then you are recommended to select Open
Read-Only as this (i) gives a clearer font for
those at the back of the room and (ii) ensures
that the text-highlighting of key words is
correct. 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-gtFull Screen)(to return to normal
view press the ltEscgt key). For more (free)
PowerPoint presentations, visit
www.physics4u.co.uk
2
Dispersion by a prism
Physics for You, 5th edition, pages 210 - 211
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
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
In fact, the ray is

• dispersed (split up into separate colours)
• like this.

7
What happens now?
Red is deviated most / least ?
least
Violet is deviated most / least ?
most
8
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 ?
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
• Physics for You, 5th edition, pages 210 - 211
• 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 whats available
http//www.physics4u.co.uk/
13
(No Transcript)
14
(No Transcript)