Optics — the section of physics studying the nature and distribution of light and also interaction of light and substance. In turn, all its sections have various practical application. Therefore the ability is so important to solve problems of optics which are very diverse and sometimes demand non-standard approaches to the decision.

## It is required to you

- - pencil;
- - ruler;
- - protractor;
- - optical formulas.

## Instruction

1. Make the explanatory drawing to a task or redraw given in a condition. At once define the perpendicular which is carried out to limit of the section of two environments to a point of falling of a beam. Note hades and refractions. It will help at the solution of tasks on environment density.

2. Learn elementary formulas: 1/d±1/f=±1/F; D=1/F; sinα/sinβ=n1/n2; =H/h=f/d. It happens so that for the successful solution of a task it is necessary to substitute these values only in one formula. d — distance from a subject to a lens, f – distance from a lens to the image, F — distance from optical center O to F focus; D – optical power of a lens; — linear increase in a lens, H – height of the image, h – subject height; α — a beam hade, β — the angle of refraction, n — the relative index of refraction of the environment.

3. At the solution of typical tasks with a reservoir or a vessel use rectangular triangles at creation of rays of light. In case of a reservoir depth which is carried out perpendicularly to a bottom of a reservoir (H), a hypotenuse — a ray of light will be a leg. In the second — legs are the parties of a vessel perpendicular each other, a hypotenuse — a ray of light. Carry out perpendiculars if the parties or depth are not enough.

4. Apply properties of adjacent and parallel corners to finding of any corner of the received triangle. Use trigonometrical function of a tangent for expression of one of sizes or finding of one of legs. A tangent of angle — the relation of the opposite party to adjacent. If hades α and refractions β are small, then tangents of these corners can be replaced with sine of the same corners. The relations of sine it will be equal to the relation of indices of refraction in environments according to the above-stated formula.

5. If the task consists in construction, then in the beginning carry out the main optical axis (the urban district o), designate the optical center (O), choose scale for focus (F) on both sides from Oh, specify also double focus (2F). In a condition the arrangement of a subject before a lens has to be specified - between F and O, between F and 2F, for 2F and so on.

6. Construct a subject in the form of the arrow perpendicular to the urban district of the lake. From the end of an arrow draw two lines - one of them has to be parallel to the urban district of the lake and pass through F, the second - to pass through the Lake. Lines can be crossed. From a point of intersection carry out a perpendicular to the urban district of the lake. The image is received. In the decision, besides construction, describe it — increased/reduced / equal; valid/imaginary, turned / direct.

7. At the solution of tasks on a diffraction lattice use a formula dsinφ=kλ where d — the lattice period (crack width), φ — the angle of diffraction (a corner between secondary waves and the falling beam perpendicular to the screen), k — number (order) of a minimum, λ — wavelength.