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1800-102-2727Let us understand a few terms before proceeding with the experiments-
Aim
To determine the focal length of:
Theory
We can obtain the focal length of a concave mirror in the following ways-
We cannot obtain the focal length of the convex mirror directly as it forms virtual, erect, and diminished images. Instead, we will use an indirect method. Using a convex lens on the concave mirror and using the same techniques with some minor changes, we can find the focal length of a convex mirror. Those changes are-
1. Use a convex lens instead of a convex mirror.
2. The image will be formed behind the screen.
3. The image formed on the screen will be an inverted image.
We can obtain the focal length of a convex lens in the following ways-
Materials Required
1. A concave mirror
2. A measuring scale
3. A screen holder
4. A mirror holder
5. A mirror stand
1. Place the mirror at a distance of 60ft from the object.
2. Both the concave mirror and the object must face each other.
3. The screen must be placed in front of the mirror. Make sure the reflecting surface is in front to form the image. Adjust the screen accordingly to get a sharp and clear image of the object.
4. Use a ruler or metric scale to measure the distance between the concave mirror and the screen. This distance is the focal length of the given concave mirror.
5. Repeat the steps to get an average of the focal length for better results.
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Let us calculate the mean of the value of the focal length for better results-
(f1 + f2 + f3) / 3 = (10 + 10 + 10) / 3 = 10cm
Result
10 cm is the focal length of the concave mirror.
1. Put the mirror and object in a well-illuminated area.
2. Place the concave mirror near the window to get a sharp image.
3. The polished mirror surface must face the object.
4. There should be no hurdle between the mirror and the object.
5. The mirror holder must be perpendicular to the measuring scale.
6. The mirror and screen must be parallel to the measuring scale.