Show formation of image (nature and size) by a convex lens with the help of a screen and candle.
Show Hint
To get a sharp image, perform the experiment in a darkened room. This will make the candle flame's image more visible on the screen. The distance from the lens to the candle is the object distance (u), and the distance from the lens to the screen is the image distance (v).
Step 1: Understanding the Concept:
A convex lens is a converging lens. When an object (like a candle flame) is placed in front of it, the lens can form a real, inverted image on a screen placed on the other side, provided the object is placed outside the focal length. The size and position of the image depend on the object's distance from the lens. Step 2: Apparatus Required:
- A convex lens with a lens holder
- A candle
- A white screen (a piece of white cardboard or a wall)
- A meter scale or optical bench Step 3: Ray Diagram and Procedure: Ray Diagram (for object beyond 2F):Procedure:
1. Setup: Place the convex lens in its holder on a table. Light the candle and place it in front of the lens. Place the screen on the other side of the lens.
2. Case 1: Object far away (beyond 2F): Place the candle at a distance significantly greater than twice the focal length of the lens. Move the screen back and forth until a sharp, clear image of the candle flame is formed on it.
3. Case 2: Object at 2F: Place the candle at a distance equal to twice the focal length. Adjust the screen to get a sharp image.
4. Case 3: Object between F and 2F: Move the candle closer to the lens, to a position between F and 2F. Again, adjust the screen to get a sharp image. Step 4: Observation:
- Case 1 (Object beyond 2F): The image formed is real (can be captured on a screen), inverted (upside down), and diminished (smaller than the object).
- Case 2 (Object at 2F): The image formed is real, inverted, and of the same size as the object.
- Case 3 (Object between F and 2F): The image formed is real, inverted, and magnified (larger than the object).
This demonstrates how the nature and size of the image change with the object's position.
