Light and Radio waves are both different frequency/wavelengths of electromagnetic radiation, which consists of two components electric and magnetic of perpendicular,
transverse waves.
Sound, on the other hand, is a
longitudinal wave which oscillates parallel to it's medium (back and forth instead of up and down).
PAL and SECAM are standards used in other countries. RGB stands for red, green, and blue - the colors of light used to create an image in a color tv set and is often used as a format name for computer monitors.
The yo-yo was first used by hunters as weapons. They were wooden disks on strings. In the 1920s, a man from the U.S. named Donald Duncan made the yo-yo into a toy after he visited the Philippines.
4. Which of the following is concerned with the study of characteristics, origin and development of land forms?