Questions

The moderate temperatures allow Earth to maintain bodies of water into its normal state.

Changes in the bodies of water in terms of volume and structure would change due to the change in temperature. 

The slot covers on a computer reduce the dust build up inside the computer. So the slot covers should be present in proper place.The missing covers can disrupt the airflow design of the case and cause overheating problems.

A periscope is an optical instrument that uses a system of prisms, lenses, or mirrors to reflect images through a tube.

Light from a distant object strikes the top mirror and is then reflected at an angle of 90 degrees down the periscope tube. At the bottom of the periscope, the light strikes another mirror and is then reflected into the viewer’s eye.

Hence, A periscope works by the principle of Total internal reflection.