light is a form of electromagnetic energy. Photons move in a wave pattern.Visible ligth is which allows you to see the colours and shapes of the objects. Can come from natural o artificial source. Can be transparent, translucent or opaque. Depens how the light travels through them. The speed of light depend on the medium. The speed in a vacuum and in the air is similar:300,000km/s. Incident ray hits the surface. Reflected ray bounces off the surface. Light is refracted when it passes from one medium to another medium with a different density. Water is denser than air. Coverging lenses. Thiker at the centre than at the edges. Concentrate rays of light. Diverging lenses thiker at the edges than at the centre. Disperse the rays of light. Red has the longest wavelength and violet the shortest. Light above the range of red infrared ligth. Light below violet ultravaiolet ligth.Sound is a form of mechanical energy produced by the vibration of material system. Travels in waves trough matter only. AIR: 340m/s. WATER:1,500m/s. IRON:5,130m/s. Cualities of sound: Intensity: sound low or soft, depending on the amplitude of the sound wave. Decibels (dB). Pitch: Higher or low depending frecuency of waves. Hertz(Hz). Tone: aloows to identify the source of a sound which has the same frecuency and intensity. Sound is reflected when a sound wave meets an obstacle. Boounces off and changes direction. Echo: Sound reflected by an obstacle. Reverberations: When a sound is reflected by an obstacle which is less than 17 m. Light pollution occurs when people and animals are exposed to contant strong light. Imposibility of seeing the night sky. Migrating birds colliding with lighted buildings. Large office blocks can be restricted to certain areas.