The tricks of light and colour.

202 Pages·1962·15.954 MB·English

by  McKay, Herbert Couchman

THE TRICKS OF
LIGHT AND COLOUR
In thisseries
TOYS AND INVENTIONS
FUN WITH MECHANICS
ODDITIES OF HEAT
ODDITIES OF SOUND
THE MAGIC OF CHEMISTRY
HALF-HOURS WITH GEOLOGY
THE TRICKS OF
LIGHT AND COLOUR
McKay
Herbert
London
OXFORD UNIVERSITY PRESS
Oxford University Press, Amen House, London E.CA
GLASGOW NSWYORK TORONTO MELBOURNE WELLINGTON
BOMBAY CALCUTTA MADRAS KARACHI LAHORE DACCA
CAFETOWN SALISBURYNAIROBI IBADAN ACCRA
KUALALUMPUR BONGKONG
Firstpublished1947
Secondimpression 1949
Thirdimpression 1957
Fourth impression 1962
Printedin Great Britain byRichard Clay and Company, Ltd.,
Bungay, Suffolk
286
—
AUTHOR’S NOTE
I HAVE been very happy writing this book.
I have tried to keep clear ofsubjects that are adequately
dealt with in school textbooks, though I have adapted
some things so as to make them suitable for home use.
I wish to acknowledge my indebtedness to my sons for
their ungrudging and unfailing help. It has been pleasant
to discuss dubious points with th—em, and indeed there are
many in this tricky and elusive and very fascinating
subject oflight.
I wish to thank also the authors and publishers of two
very charming books Light and Colour in the Open Air^
:
by M. Minnaert (Bell) and Adaptive Coloration in Animals,
by Hugh Cott (Methuen).
CONTENTS
CHAP. PAGE
Author’s Note • • 5
L How We See • • 7
n. Candlepower and the Fading of Light . 32
m. Light Waves 47
.
IV. The Spkd of Light . 69
V. Seeing in the.Dar.k .. . 79
VI. Shadows .... . 93
VII. Colours . 108
vm. How Light is Reflected . 122
IX. How Light is Refracted . 143
X. Optical Illus.ions.. .. . 161
XL Camouflage . 183
CHAPTER
1
HOW WE
SEE
(Try to answer these questions first)
What is the retina?
In what direction do we see objects?
How
does a sailor use landmarks?
Why is an astronomer a “ super-range-finder ”?
What is binocular vision?
Which is your dominant eye?
How do tnc eyes act as range-finders?
How
does the stereoscope act?
How can we get a stereoscopic effect from a single
picture?
How do artists get stereoscopic effects?
What is an ana^yph?
What is meant by “parallax ”?
How is the parallax ofstars measured?
How does a pinhole form an image?
Why are circles oflight often seen under trees?
How
is a pinhole camera for taking photographs
made?
How
does closeness affect apparent size?
What is the least distance ofdistinct vision?
We look at a tree, and admire its sturdy trunk. We see
the many colours of the foliage that seem never twice
alike. We see! That is the amazing thing we so easily
take for granted. We see—but how do we see? Why
do we see?
It seems that light from the tree enters the eye, and
forms an image on a little screen at the back of the eye
7