~
Shadow formation by a point light source
~/WE~--------------------------------------------~~
Observations
Behind the opaque body an area remains unlighted: a
shadow is formed. The smaller the distance between body
and light source, the larger the shaded area.
The shadow is sharply delimited.
Show that a shadow is formed behind an opaque body,
whose area is a function of its distance from the light
source.
Materials
Magnet optics panel,
Lamp, halogen, 12 V I 50 W
Model earth/moon
Var. transformer
08270.00
08270.20
08270.07
13533.93
1
1
1
1
Evaluation
When light from a point light source strikes an opaque
body, a sharply delimited shadow is formed behind the
latter.
The smaller the distance of the opaque body from the light
source, the larger the shaded area.
Shadow formation is a result of the rectilinear propagation
of light.
To depict the shaded area, it is generally sufficient to draw
the marginal rays.
The marginal rays have an intersection point in the point
light source.
Apparatus and methods
- Set the magnetic lamp onto the magnet panel, push
up the cover at the back of the lamp producing a
divergent light beam with a point light source.
Place the earth model in the light beam in such a way
that the part of light beam still passes by the model;
observe the shadow (Fig. 1).
- Move the earth model towards and away from the light
source and watch the shadow while doing so.
Fig. 1
~0~
//
50
/
40
I
/
/
/
/
®
30
'-.._
\
"""
20
~
...........
•
""
10
10
20
~Q
40
50
60
/
70
........
"'~~--80
PHYWE Series of publications • Physics Dem. Exp. • Magnet Board Optics • PHYWE SYSTEME GMBH • 37070 Gottingen , Germany
11001
15
~
Shadow formation by a point light source
~~------------------------------------------------~~~--f~VWE~
Space for notes
16
11001
PHYWE Series of publications • Physics Dem. Exp. • Magnet Board Optics • PHYWE SYSTEME GMBH • 37070 Gottingen , Germany