III. Answer the questions:

1. When does scattering take place 7 (What does scattering of incident light result from?) 2. Why may we consider a surface to be either polished or unpolished at the same time? 3. In what case is it possible to consider a surface as polished? 4. Do rays of the invisible region of the spectrum undergo reflection as well as those of the visible one? 5. Which rays of the visible region of the spectrum have the longest wavelength, and which the shortest? 6. Are mirrors scarce in your hostel? 7. Do you know what the word scarcely mean? Can you translate the following: I can scarcely understand you because your accent is different from ours.

Selective Reflection

I. Translate:

1. Not a single man has seen our planet from the outside of our atmosphere before Gagarin, and no man had seen it from the outside of a spaceship before Alexei Leonov stepped out of the Voshod-2 spaceship. 2. No trace (след) has been found so far of the man that brought his short story intended for the contest (конкурс) and then disappeared. 3. This problem seems to be a purely mathematical proposition.

II. Answer the questions:

1. What does the percentage of light reflected by a mirror depend on? 2. Is there any substance that reflects light of only one wavelength? 3, Is there any substance that reflects light of all wavelengths? 4. What color does such a substance appear to be seen in a white light? 5. What substances seem to be colored when we see them illuminated by white light?

III. Say a few words about selective reflection.

Concave Spherical Mirrors

I. Translate and memorize: a) to follow, the following, as follows:

1. Day follows night, just as spring follows winter. 2. Warm weather was followed by a long period of cold and rains. 3. A camera lens with a relative aperture of f/3 collects four times as much light as one with a relative aperture of f/6; it follows that the former is four times as fast for taking pictures as the latter. 4. A concave spherical mirror may be described as follows: it is a part of a spherical shell, the inner surface of the latter being polished. 5. Among many instruments Petrov spoke about in his report, the following seemed to be of the greatest importance: the aerial camera, the range finder, the telescope and the microscope.

II. Answer the questions:

1. What is a spherical mirror? 2. How would you describe a concave spherical mirror? 3. Which side/surface of the sphere the mirror is a part of is silvered? 4. What point of the mirror do we call the vertex of the mirror? 5. What straight line do we call the principle axis of the mirror? 6. What do we call the straight line passing through the vertex of the mirror and its center of curvature? 7. What is any straight line from the center of curvature to the mirror perpendicular to? 8. How will the first of the two rays, UM and UP, strike the mirror? 9. In what direction will it be reflected? 10. In what way will the other ray, i.e. UP, be reflected? 11. What will these two reflections result in? 12. What angles will the incident ray and the reflected ray make with the radius of curvature? 13. Arc both rays reflected through the same point? 14. How can one define the reflection between the points V and U? 15. What is the necessary condition for all the rays from U to pass through V? 16. Can the change of position of the point U alter (=change) this reflection or does it hold in all cases?

III. Speak about a concave spherical mirror.