The figure (Figure 1) shows a small plant near a thin lens. The ray shown is one

Question

The figure (Figure 1) shows a small plant near a thin lens. The ray shown is one of the principal rays for the lens. Each square is 1.5 cm along the horizontal direction, but the vertical direction is not to the same scale. Use information from the diagram to answer the following questions:

a)What is the focal length of the lens? Express your answer using two significant figures. (f= ___cm)

b)Calculate where the image should be. Express your answer using two significant figures. (s'=___cm)

Explanation / Answer

When we see the emergent light ray which is parallel to the optic axis, the incident ray come from focus only.

Hence the focal lenght should be f= 3x1.5 = 4.5cm

The image should be formed at infinity only, if the object is at focus.

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