The role of lenses on light in the second year of junior high school

The density of the hesitant air is different from that of the mirror, causing the refraction of light. And because the angle between the convex lens and the concave lens and the incoming light is different, one converges and the other diverges.

Because the image distance (20cm) > object distance (10cm), and the image is on the light screen, according to the imaging law of the convex lens, it can be known that the image is a real image magnified by inverted. The object distance must be greater than one time the focal length is less than two times the focal length, and the image distance must be greater than two times the focal length, that is, 2f>10cm>f 20cm>2f at the same time, and the range of the focal length of the convex lens can be obtained by solving the two inequalities 10cm>f>5cm

It looks like an upside-down enlarged image. The object distance must be greater than one time the focal length and less than two times the focal length. 2F>10cm>F 20cm>2F.

Solving the two inequalities yields the range of focal lengths of the convex lens is 10cm>f>5cm

Because the image is formed, the image distance is 20cm> the object distance is 10cm, and the imaging is an inverted magnified real image.

Two inequalities are obtained: i.e., 2f>10cm>f; 20cm>2F, 10cm>F>5cm

According to the object distance 10 is less than the image distance 20, it can be known that the image formed is an inverted magnified real image, so the object is between one time the focal length and two times the focal length, so 10 is greater than one time the focal length is less than two times the focal length, and then the image distance is outside the two times the focal length, that is, 20 is greater than the two times the focal length, and the focal length range of the two relations together to solve the inequality is greater than 5 and less than 10

Convex lenses can be used in (4) main types of images.

The camera lens acts as a (convex lens), and the light from the object converges on the film through the lens to form a (reduced) and (inverted) (real) image.

Question 1: There are four types of real images: inverted and reduced real images, inverted and other large real images, inverted magnified real images, and upright magnified virtual images.

Question 2: Convex lens; Handstand shrinks solid.

The direction of light propagation through the center of light does not change.

2) The light rays parallel to the main optical axis are refracted and overfocused.

3) The light rays that have passed through the focal point are refracted and parallel to the main optical axis.

The direction of light propagation through the center of light does not change in the concave lens (1).

2) The reverse extension line of the ray refracted by the ray parallel to the main optical axis crosses the virtual focus, and (3) the ray rays directed at the virtual focus are refracted and parallel to the main optical axis.

The convex is the convex, the concave astigmatism!

The direction through the main axis is unchanged, the direction through the convex lens is deflected towards the main axis, and the deflection through the concave lens is off-axis.