Part 79

12. (Pg. 170) Upon what does the real velocity of a body, depend?

13. (Pg. 171) What must be known, to enable us to ascertain the real space contained in a degree?

14. (Pg. 171) What is explained by fig. 2, plate 17?

15. (Pg. 171) What is said respecting the evidence afforded by our senses, and how do we correct the errors into which they would lead us?

16. (Pg. 171) An image of a visible object is formed upon the retina of each eye, why, therefore, are not objects seen double?

17. (Pg. 172) By what experiment can you prove that a separate image of an object is formed in each eye?

18. (Pg. 172) Under what circumstances are objects seen double?

19. (Pg. 172) Why is not the image of an object inverted in the common mirror?

20. (Pg. 172) Your whole figure may be seen in a looking-glass, which is not more than half your height; how is this shown in fig. 3. plate 17?

21. (Pg. 173) Why is the image invisible to the person, when not standing directly before the glass?

22. (Pg. 173) In what situation may a second person see the image reflected?

23. (Pg. 173) In what direction will an object always appear to the eye?

24. (Pg. 173) How is this explained by fig. 4, plate 17?

25. (Pg. 173) What is it that reflects the rays in a looking-glass?

26. (Pg. 174) All opaque bodies reflect some light, why do they not all act as mirrors?

27. (Pg. 174) What substances form the most perfect mirrors, and for what reason?

28. (Pg. 174) What are the three kinds of mirrors usually employed for optical purposes?

29. (Pg. 174) How are the rays of light affected by them?

30. (Pg. 175) What is the form of a convex mirror, and how do parallel rays fall upon it, as represented in fig. 1, plate 18?

31. (Pg. 175) What is represented by the dotted line in the same figure?

32. (Pg. 175) Explain by the figure, how the parallel rays will be reflected.

33. (Pg. 175) At what distance behind such a mirror, would an image, produced by parallel rays, be formed?

34. (Pg. 175) What is that point denominated?

35. (Pg. 176) What is meant by a focus?

36. (Pg. 176) Why is the point behind the mirror, called the imaginary focus?

37. (Pg. 176) Why does an object appear to be lessened by a convex mirror, (fig. 2.)?

38. (Pg. 176) What is a concave mirror, and what its peculiar property?

39. (Pg. 176) How are parallel rays reflected by a concave mirror, as explained by fig. 3, plate 18?