Question

4. Draw the ray diagram to show the image formed by a convex lens with focal length5cm when the object is placed 15 cm from the lens. What is the magnification?

Answer 1

In order to draw the ray diagram, let's draw two rays: one parallel to the lens axis, which will pass through the focus of the lens, and one passing through the center of the lens.

Drawing the ray diagram of this question, we have:

In order to calculate the magnification, first let's calculate the image position:

`\begin{gathered} (1)/(f)=(1)/(d_o)+(1)/(d_i)\\ \\ (1)/(5)=(1)/(15)+(1)/(d_i)\\ \\ (1)/(d_i)=(3)/(15)-(1)/(15)=(2)/(15)=(1)/(7.5)\\ \\ d_i=7.5\text{ cm} \end{gathered}`

The magnification is given by:

`M=-(d_i)/(d_o)=-(7.5)/(15)=-0.5`