If your camera has a zoom ring on the lens, you can turn it during a slow exposure to streak lights.
Most fixed lens cameras have a built-in zoom lens and zooms are also very popular with SLR users. These lenses are popular because they let you choose any focal length within the range the lens is designed for. The range is indicated in mm and on some fixed lens cameras as a multiple. For example, a camera with a range of 28-90mm is also called a 3x zoom (90 divided by 28 is about 3). A lens with a zoom range of 6-72mm would be called a 12x lens (72 divided by 6 is 12).
HOW TO: ZOOMING THE LENS
To zoom on most fixed lens cameras you press a lever in one direction or press a zoom-out button to widen the angle of view. You press the lever in the other direction, or press a zoom-in button to enlarge subjects. On SLRs and some fixed lens cameras you turn a ring on the lens.