1. lenses with thick edges and thin edges are convex lenses
2. The methods to distinguish convex lens and concave lens are as follows: ① "touch": distinguish by comparing the thickness of lens * and edge; ② "Look": distinguish whether the imaging of the observation lens is enlarged or reduced by approaching the object; ③ "Illumination": distinguish whether parallel rays converge or diverge through a lens; ④ "Shaking": read the text on the book through the lens, shake the lens,Flat window,Manufacturer of spherical lens see the shaking direction of the image and the shaking direction of the lens. (concave lens in the same direction and convex lens in the opposite direction)
3. (1) main optical axis: a straight line passing through the spherical center of the lens sphere. (2) Optical center: the center of the lens.
(optical center is a special point on the main optical axis of the lens, and the propagation direction of light passing through it does not change) 4. (1) focus: the light parallel to the main optical axis converges at a point F on the main optical axis after being folded * by the convex lens, which is called focus. (one on the left and one on the right) (2) focal length: the distance from the optical center to the focus. It is expressed by F (the left and right focal lengths are equal) (the focus of the concave lens is the intersection of the reverse extension line of the folded * light, so it is the virtual focus)
4. Estimate the focal length of convex lens (hyperopia glasses) by experimental method: face the hyperopia glasses directly to the sunlight, put a piece of paper on the other side, move back and forth until the spot on the paper becomes the smallest and brightest, Flat window,Manufacturer of spherical lensmeasure the distance from the smallest and brightest spot to the hyperopia glasses, and record it, which is the focal length.
Oral memory method:
(1) Double focal length internal and external division virtual and real (2) double focal length internal and external division amplification and reduction (3) the real image must be inverted, and the image object is on the opposite side of the lens. The virtual image must be upright, and the image object is on the same side of the lens. (4) When forming a real image, the object distance decreases and the image distance increases. It can be remembered that things are near, images are far, and images become larger.
5. In the experiment of "exploring the imaging law of convex lens", Flat window,Manufacturer of spherical lenscandles, convex lens and light screen are placed in turn from left to right. First, make them on the same straight line, and then adjust their height to make their centers roughly at the same height. The purpose of this is to form a complete and clear real image in the center of the light screen.
6. Real image: the image that can be presented on the light screen. It is formed by the convergence of actual light.
