Question and Answer 6

P62

1.The light travels faster than sound.

2.The sound wave creates pressure.

3.The light waves travel further through air than sound.

4.The sound waves travel further through sea than light.

P64

1.A laser amplifies light using a special material - s crystal such as a ruby, or a gas, such as, CO2 - formed into a cylinder with mirrors at each end.

2.Lasers are used in communication in many ways, such as scanning bar codes at checkout lines, transferring information by reading CDs and DVDs, and tapping the fiber optic backbone of phone and Internet services, explains Nicholas Gerbis on Howstuffworks

3.This material can be excited to a semi-stable state by light or an electric discharge. The material can be a crystal, glass, liquid, dye, or gas as long as it can be excited in this way.

P65

1.Many scientific, military, medical and commercial laser applications have been developed since the invention of the laser in 1958. The coherency, high monochromaticity, and ability to reach extremely high powers are all properties which allow for these specialized applications.

P67

1.The Hubble Space Telescope (HST) is a space telescope that was launched into low Earth orbit in 1990, and remains in operation. Although not the first space telescope, Hubble is one of the largest and most versatile, and is well known as both a vital research tool and a public relations boon for astronomy.

2.Roughly eighty percent of all the mass in the Universe is made of dark matter – a mysterious invisible substance responsible for the structure of galaxies and the patterns of the cosmos on the very largest scales.