Chapter Name: Human Eye and Colourful World
Activity Name: Object movement in Human Eye and Colourful World
This experiment explores the concept of the least distance of distinct vision by observing changes in the clarity of printed letters on a text book when it is moved closer and farther away from the eyes.
Textbook, ruler or measuring tape, friends to assist in measurements.
Step by Step Procedure:
- Hold the text book in front of you at a certain distance.
- Attempt to read the contents on the page.
- Slowly move the book towards your eyes until it is very close.
- Observe and note down any changes in the appearance of the printed letters or strain in the eyes.
- Move the book backward until you can see clear printed letters without straining your eyes.
- Ask your friend to measure the distance between your eye and the text book at this position and note down its value.
- Repeat the activity with other friends and note down the distances for distinct vision in each case.
- Find the average of all these distances to determine the average least distance of distinct vision.
- Participants will observe that when the text book is moved too close to the eyes, the printed letters appear blurred, and they might feel eye strain. However, when the book is held at a certain distance, they can see the letters clearly without any discomfort.
- Ensure the text book is well-lit to avoid unnecessary strain on the eyes.
- Take breaks between repetitions to prevent eye fatigue.
- Avoid forcing the eyes to focus at extreme distances to prevent any harm.
Lesson Learnt from Experiment:
The experiment demonstrates that to see an object comfortably and distinctly, it is necessary to hold it at a certain distance from the eyes. This distance is known as the least distance of distinct vision.
The value of this distance varies from person to person and with age. Younger individuals tend to have a smaller least distance of distinct vision (around 7 to 8 cm), while in old age, it increases significantly (around 1 to 2 meters or more).