The screen of a pinhole camera is a square of side 160mm and it is 150mm behind the pinhole. The camera is placed 11m from a pole from a pole and positioned so that the image of the pole is formed centrally on the screen. The image occupies three-fourth of the height of the screen. What is the height of the pole. (explanation needed please)
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Answer:
The side of the screen pinhole is
a
=
0.16
m
The distance from the pinhole to the screen is
d
=
0.15
m
The distance from the flag to the pinhole is
D
=
11
m
The expression of the scale factor is given by,
f
=
d
3
4
(
a
)
Substitute all the values in the above equation.
f
=
(
0.15
m
)
(
3
4
)
(
0.16
m
)
=
1.25
The expression of the height of the flag-staff is given by, H'
=Substitute all the values in the above equation.
H = 11 1.25
= 8.8 m
Thus, the height of the flag-staff is 8.8 m.
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