Tips for using image lens
The usage techniques of image lens (such as magnifying glasses and camera lenses) mainly include the following points:
Focusing method
Sunlight focusing method: Place a convex lens directly facing the sunlight, adjust the position so that the light is focused on the paper to form the smallest and brightest spot, which is the focal point.
Object observation method: When observing an object through a convex lens, it is necessary to maintain the object distance less than twice the focal length (u<f), and at this point, a vertical and magnified virtual image is formed.
Application of imaging laws
Magnifying objects: The closer the object is (u<f), the larger the image; The farther the distance between objects (u>f), the smaller the image.
Camera imaging: When the object distance is greater than twice the focal length (u>2f), it forms an inverted and reduced real image, suitable for capturing distant objects.
Projector imaging: When the object distance is less than twice the focal length but greater than one focal length (1f<u<2f), it forms an inverted and magnified real image.
Lens selection and adjustment
Magnifying glass: When observing small objects, try to stay as far away from the object as possible but not exceed one focal length.
Projector lens: By adjusting the distance between the lens and the screen to change the size of the image, the lens can be moved away from the screen to increase the size of the image.
Special usage scenarios
Flat convex lens: If used for laser focusing, light should be incident from a convex surface to reduce spherical aberration; If used for collimated light, it is incident from a plane.