Explain by an activity how to find
focal length of Concave mirror in laboratory ?
physics
Answers
How to find the focal length of convex lens?
Following are the ways to obtain the focal length of convex lens:
The convex lens is thicker in the middle and thinner at the edges and is also known as the converging lens.
The refracted rays from the parallel beam of light converge on the other side of the convex lens.
If the image is obtained at the focus of the lens, the image would be real, inverted and very small.
f is the focal length which is the difference between the optical centre of the lens and the principal focus.
The image can be obtained on the screen as the image formed by the lens is real.
To determine focal length of a given concave mirror
Materials Required
A concave mirror
A measuring scale
A screen holder
A mirror holder
A mirror stand
Procedure
The distance between the selected distinct object should be more than 50 ft.
The concave mirror placed on the mirror stand and the distant object should be facing each other.
The screen should be placed in front of the reflecting surface of the mirror. To obtain a clear, sharp image the screen should be adjusted.
Using a metre scale the distance between the concave mirror and screen can be determined. The distance is the same as the focal length of the given concave mirror.
Repeat the above procedure thrice to calculate the average focal length.
Using a metre scale the distance between the concave mirror and screen can be determined. The distance is the same as the focal length of the given concave mirror.