Image Formation by a Convex Lens

To find the image distance for varying object distances in the case of a convex lens and draw corresponding ray diagrams to show the nature of the image formed. 

1. Fix a thin convex lens on a lens holder and place the screen on the other side of the lens. 

2. Focus a sharp, clear, inverted image of the distant object on the screen. This is the rough focal length, measure it with the help of a metre scale. 

3. Mark the position of the lens on the optical bench or a table. Fix the lens at this point, and label it as ‘O’. 

4. Mark a point ‘F’ at both sides of the lens as the focus of the lens by knowing the focal length as calculated in the first step. 

5. Mark a point 2F at both sides of the lens, the distance of 2F from the lens is double the focal length of the lens. 

6. Place a candle on the table or needle on the optical bench at a distance beyond 2F and adjust the height of the centre of the lens nearly equal to the height of the flame of the candle. 

7. To locate a sharp image of the candle flame in the convex lens from the other side of the lens, adjust the screen's position and record your observations. 

8. Now, place the object, e., the lighted candle or the needle at 2F and record your observations. 

9. Now, shift the object between F and 2F and record the observations. 

10. Now, place the object at F and record the observations. 

11. Place the object between O and F of the lens and record your observations. 

12. Draw ray diagrams for all the positions of the object.