First go to this lesson: https://asupd-implementation-production.s3.amazonaws.com/Course-Content/Storyline+Files/Physics/Unit+L/L03/story_html5.html
then The objective of this assignment is to explain how an image is formed using ray diagrams and how changing the ray diagram parameters (the object’s height, the distance from the lens, and the lens’ focal length) affects how the image appears (real or virtual, magnified or diminished, and upright or inverted).
Instructions
This assignment will be a bit different from other assignments in this course. You will be given questions that you’ll need to work through carefully by drawing ray diagrams in your notes. The objective is for you to draw the principal rays given specific parameters. You will reproduce the image given to scale, using the given ruler on the diagram to measure the height of the object and also where and how the image will appear. You are welcome to use your own scale. Remember to draw your diagrams with plenty of space around so you can draw a clear, precise, and efficient ray diagram. Answer the associated essay questions using complete sentences and paragraphs, and be sure to use precise terminology from class to support your answers. Please include all ray diagrams in your answers!
Question 1  Given the double convex lens and the object below, answer the following questions to describe the image:
A horizontal ruler from 0 to 100. An image of an upward pointing arrow in a frame, at 0. A double convex lens at 100. X marked in the center of the ruler. 
What does the “X” on the horizontal line represent?
Draw the ray diagram in your notes, showing only the principal rays. Explain why you don’t need to draw more rays.
Where will the image appear? On the left or on the right of the lens? At which mark on the ruler?
How will the image look? Upright or inverted? Same size, larger, or smaller?
Question 2 
Now make a separate drawing and place the bottom of the arrow on the 20 cm mark. Describe what happens to the image (use the adjectives: real or virtual, magnified or diminished, and upright or inverted).
Question 3 
Now place your object on the focal point of the lens. What happens to the rays when they leave the lens? Do you think you can see an image? Why or why not?
Question 4 
Now move the object between the lens and focal point, at the 70 cm mark for example. What happens to the image now? What real life application of this phenomenon can you think of?