7S. Why do photographs acquire relief and depth when looked at through a magnifying glass or in a concave mirror? 79. Why is it best to seat oneself in the middle of a movie-house? SO. Why is it better to look at a painting with one eye? 81. How does a stereoscope work? 82. How can we see things like the giants in fairy tales? 83. \Vhat is a telestereoscope? 84. Why do th ings sparkle? 85. Why does the landscape acquire deeper relief when viewed from a passing train? 86. How are stereoscopic photographs of celestial objects taken? 87. \Vhat is the effect of the so-called "shad ow marvel" based on? 88. What colour does a red flag assume in blue light? 89. What is irradiation and astigmaLism? 90. What kind of pictures follow you with their eyes? And why? 91. Is it a person with normal eyesight or a short-sighted person who thinks the bright. stars bigger? 92. When you hear the echo 1.5 seconds after you clap your hands, how far away is the sound barrier? 93. Are there such things as sound mirrors? 94. Where does sound propagate faster, in air or in water? 95. To what technical uses can echoes be put? 96. Why does a bee buzz? fl7. Why is it so hard to spot a chirring grasshopper? 98. What transmits sound bettor-air or some denser medium? 99. What is ventriloquism based upon?
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There is a second part to this book. However, both can be read independently of each aLher.