Junior 3 Physics Questions Magical Eyes

For cameras, it is necessary to understand the variation of object distance, image distance and image size, and remember one rule: the smaller the object distance, the larger the image distance, and the larger the image size; Conversely, the larger the object distance, the smaller the image distance, and the smaller the image distance.

The object is not imaged in focus, and the double focal length is the same.

It is smaller than the inverted two-focal pointstand, and the slide show is placed outside the focal point and inside the two.

The object is placed in focus, and a large virtual image is seen on the opposite side.

If the image can be presented on the screen, it must be a real image in handstand.

1 U f becomes a real image, u f becomes a virtual image, and the focus is the dividing point between the real image and the virtual image.

2 U 2F becomes a zoomed real image, U 2F becomes a magnified real image, and the double focal point is the dividing point between magnified real image and reduced virtual image.

3 When the object distance decreases, the image distance becomes larger, and the image becomes larger; When the object distance increases, the image distance becomes smaller, and the image becomes smaller.

4 When a real image is formed, the image and the object are on the opposite side of the convex lens, and when the image is a virtual image, the image and the object are on the same side of the convex lens.

5 The real image is formed by the convergence of the actual light and can be displayed on the light screen, while the virtual image is the intersection of the reverse extension line of the actual light and is not displayed on the light screen.

This is the principle of convex lens imaging, and there is a diagram in it.

Problem solving ideas: According to the experimental phenomenon and process in the problem, it can be seen that when the "myopia glasses" in front of the convex lens are removed, the light screen that undertakes the clear image of the candle flame should be close to the convex translucent fiber.

It shows the role of "myopia glasses" - it has a divergent effect on light, and myopia glasses are concave lenses; It indicates that myopic eyes have a strong effect on the convergence of light. It means that when the myopic eye wears glasses, it looks like it is on the retina, and when it does not wear glasses, it looks like it is in front of the retina.

Answer: Myopic glasses have a divergent effect on light Myopia glasses are concave lenses Myopic eyes have a stronger convergence ability than ordinary eyes The image of myopic eyes is in front of the retina.

Miraculous"Eyes"

1. The imaging principle of the magnifying glass:When the object is within the focal length, the convex lens forms an upright and magnified virtual image.

2. Microscope

Structure: eyepiece, objective.

Imaging principle: the objective lens is inverted and magnified. The eyepiece is equivalent to an ordinary magnifying glass, which magnifies the real image into a virtual image again.

3. Telescopes

Structure: eyepiece, objective.

Imaging principle: the objective lens becomes an inverted and reduced real image, and the eyepiece is equivalent to an ordinary magnifying glass, which magnifies the real image into a virtual image again.

4. Camera

Structure: lens, aperture, shutter, film.

Imaging principle: When the object distance is greater than twice the focal length, the convex lens becomes an inverted and reduced real image.

5. Projector

Disturbance structure: convex lens, plane mirror, screen.

Imaging principle: When the object distance is between the focal length and two times the focal length, the convex lens becomes an inverted and magnified real image.

Hope above the face of physics about the magical"Eyes"With the explanation and learning of knowledge, students can grasp the potato rot well and achieve excellent results in the exam.