Given:
The focal length of the concave lens is f = -5 cm
The object distance from the lens is u = -15 cm
Required:
Ray diagram
Magnification
Explanation:
The rules related to incident ray and reflected ray are:
1) Any incident ray moving parallel to the principal axis will pass through focus after reflection.
2) Any incident ray passing through the focus will move parallel to the principal axis after reflection.
3) Incident ray passing through the optical center will reflect undeviated.
The ray diagram is shown below
Here, yellow lines represent incident rays passing parallel to the principal axis and the reflected ray passing through the focus.
The maroon line shows the incident ray passing through the optical center and the undeviated reflected ray.
The green color is the object and image.
In order to find magnification, first, we need to calculate the image distance given as
[tex]\begin{gathered} \frac{1}{v}-\frac{1}{u}=\frac{1}{f} \\ \frac{1}{v}=\frac{1}{f}+\frac{1}{u} \\ =-\frac{1}{5}-\frac{1}{15} \\ v=-3.75\text{ cm} \end{gathered}[/tex]The magnification will be
[tex]\begin{gathered} m\text{ = }\frac{v}{u} \\ =\frac{-3.75}{-15} \\ =0.25\text{ } \end{gathered}[/tex]Final Answer: Thus, the magnification is 0.25 which means the size of the image is 0.25 times the object.
