In the 20th century, new types of glass such as laminated glass, reinforced glass and glass bricks have increased the use of glass as a building material and resulted in new applications of glass. Multi-storey buildings are frequently constructed with curtain walls made almost entirely of glass. Similarly, laminated glass has been widely applied to vehicles for windscreens. While glass containers have always been used for storage and are valued for their hygienic properties, glass has been utilized increasingly in industry. Optical glass for spectacles has been used since the late Middle Ages. The production of lenses has become increasingly proficient, aiding astronomers as well as having other application in medicine and science. Glass is also employed as the aperture cover in many solar energy systems. COUNT 5
QSN1 What type of glass is used in cars? ANS1 laminated QSN2 When did eyeglasses originate? ANS2 late Middle Ages QSN3 The walls of skyscrapers are often made of what material? ANS3 glass QSN4 What type of power systems use glass? ANS4 solar QSN5 What type of scientists rely on glass for distant observations? ANS5 astronomers