Thin lens focal length experiment

Experiment 29 The focal length of the thin lens

【Purpose requirement】

1. Learn the coaxial adjustment of optical components;

2. Master the basic method of measuring the focal length of thin lenses;

3. Deepen the understanding of the imaging rules of thin lenses.

【Experimental Principle】

1. Measurement of the focal length of the thin lens

1. Measurement of the focal length of the convex lens; (1) Object image distance method; (2) Displacement method; (3) Autocollimation method (planar mirror method);

2. The object image distance method measures the focal length of the concave lens;

Second, the coaxial adjustment on the optical bench

In order to reduce the error of the focal length measurement, the optical elements must be adjusted coaxially. The adjustment of the coaxial axis can make the light into paraxial light and reduce the aberration. Otherwise, the quality of the image will be reduced, and even the "light path will be blocked". Coaxial adjustment is a basic requirement that all optical experiments must meet.

【Experiment content】

1. Use the displacement method to measure the focal length of the convex lens;

2. Use the parallax method to measure the focal length of the convex lens;

3. Use the self-collimation method to measure the focal length of the convex lens;

4. Study the imaging rule of convex lens;

5. Measuring the focal length of the concave lens with the object image distance method;

6. Use the self-collimation method to measure the focal length of the concave lens.

【Instruments】

Serial number

equipment name

Model / Specification

Unit price (yuan)

Remarks

1

Teaching optical bench

1000 × 80 × 35mm

1000

Compatible with other experiments

2

Slide 1

Fixed socket

360

3

Slide 2

With lateral displacement,

Moving range ± 4mm

4

Slide 3

With horizontal and vertical displacement,

Moving range ± 4mm

5

Extended light source

12V, 21W

480

6

Convex lens / concave lens

Φ40 f 100 / Φ40 f -50

700

7

Plane mirror

Φ36 × 4, dielectric coating

8

Frosted glass or imaging screen

80 × 60mm

9

Object screen, needle tip

80 × 60mm / Φ10mm