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1
OBSERVATIONS
Figure 1
Figure 2
f(cm)
R
1
=R
2
(cm)
Measured
12.3
13.6
Calculated
13.6

% Difference
9.5588%

Table 1
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DISCUSSION
In this lab experiment we explored how the properties of a concave lens behaves according to it focal
point by looking at its diverging rays of the ray beam. And also from this lab experiment we could get
to know the Lensmaker’s Equqtion and how to calculate the focal length using that equation.
Theories
Diverging parallel rays trace back to the focal point. The light does not actually pass through the focal
point. So that we can’t make a fire focusing sunlight with a diverging lens.
Lensmaker's equation
The focal length of a lens
in air
can be calculated from the lensmaker's equation:
where
f
is the focal length of the lens,
n
is the refractive index of the lens material,
R
1
is the radius of curvature of the lens surface closest to the light source,
R
2
is the radius of curvature of the lens surface farthest from the light source, and
d
is the thickness of the lens (the distance along the lens axis between the two surface vertices).
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 Spring '11
 PERERA

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