The reason why : $b a careful collection of many hundreds of reasons for things which, though generally believed, are imperfectly understood. A book of condensed scientific knowledge for the million — John Stuart Mill — John Shaqi
The reason why : $b a careful collection of many hundreds of reasons for things which, though generally believed, are imperfectly understood. A book of condensed scientific knowledge for the million
John Stuart Mill · en
Take a marble and roll it across the floor, so that it shall
strike the wainscot obliquely. Let A in the diagram represent the
point from which the marble is sent. The marble will not return to
the hand, nor will it travel to the line B, but will bound off, or
be _reflected_, to C. Now B is an imaginary line, _perpendicular
to the reflecting surface_; and it will be found that the path
described by the marble in _rolling to the surface and rebounding
from it_, form, with the line B, two angles that are _equal_.
These represent the angles of _incidence_ and of _reflection_,
and explain why the reflection of a person standing at A before a
mirror, would be seen by another person standing at C. This simple
law in optics explains a great many interesting phenomena, and
therefore it should be clearly impressed upon the memory.
[Verse: "And God made two great lights; the greater light to rule
the day, and the lesser light to rule the night: he made the stars
also."--GEN. I.]
523. _Why do windows reflect the sun in the evening?_
Because the eye of the observer is in the _line of the reflection_.
524. _Why do windows not reflect the sun at noon?_
They do, but our eyes are not then in the _line of the reflection_.
[Illustration: Fig. 15.--SHOWING THE LINES OF INCIDENCE AND REFLECTION
OF THE SUN'S RAYS AT NOON AND AT EVENING.]
It is obvious from the foregoing diagram that the evening rays of
reflection fall upon the eyes of spectators, while the reflections
at noon are so perpendicular that they are lost.
525. _Why do the sun and moon appear smaller when near the meridian,
than when near the horizon?_
Because, when near the horizon, they are brought into _comparison with
the sizes of terrestrial objects_; but when near the meridian they
occupy the centre of a vast field of sky, and as there are no objects
of comparison surrounding them, they _appear smaller_.
[Verse: "There is no darkness nor shadow of death, where the workers
of iniquity may hide themselves."--JOB XXXIV.]