RAYS & WAVES REFLECTION OF LIGHT What is light? Light is a form of radiation. ie Light radiates from its source. It is produced by the Sun, and by objects such as light bulbs and matches. Light carries energy and travels as a wave. Light travels at a speed of 300,000,000 metres per second. Light waves travel in straight lines. Light can travel through empty space. Seeing luminous objects A luminous object gives out light and can also be called a light source. How does light from a light bulb and other light sources reach your eye? Light travels in a straight line directly into your eye. Reflective materials Objects that reflect light well: ⚫ Have smooth, shiny surfaces and are usually pale colours. ⚫ Give clear images because they reflect light regularly. Objects that do not reflect light well: ⚫ Have rough, matt surfaces are usually dark colours. and ⚫ Give diffuse images (or do not give any images) because they reflect light irregularly. This is called scattering. Seeing non-luminous objects Objects that do not give out light are non-luminous. How does your eye see non-luminous objects such as a book? Light from the light source strikes the book and some of the light is reflected into your eye. Reflection in plane mirror Normal Incident ray Angle of incidence Angle of reflection Reflected ray REMINDER: always use a ruler to draw light rays (light travels in straight lines) and don’t forget to include arrows showing direction of light. Plane mirror Laws of reflection: 1. The angle of incidence is equal to the angle of reflection. 2. The incident ray, the reflected ray and the normal all lie in the same plane (i.e. the two rays and the normal can all be drawn on a single sheet of flat paper). Reflection in plane mirror A plane mirror reflects light regularly so it produces a clear image, which is the same size as the object. The image appears the same distance behind the mirror as the object is in front of it. What is different about the image compared to the object? When an object is reflected in a plane mirror, left appears as right and right appears as left. This type of reversal is called lateral inversion. Image formed in a plane mirror Image formed in a plane mirror Image formed in a plane mirror The image in the mirror looks the same as the object, but it is laterally inverted (back to front). The image formed is upright, but it is a virtual image (doesn’t really exist). Virtual Image When you look at a mirror you see a virtual image that appears to be behind the mirror. The image appears to be the same size as the original object and the same distance behind the mirror as the object is from the mirror. It is also laterally inverted IMAGES WHICH CANNOT BE CAUGHT ON A SCREEN distance distance object virtual image Lateral Inversion Normal view from the front. Same view as seen in the rear view mirror of a car. The word AMBULANCE is laterally inverted so that it reads correctly when seen in a driving mirror. Finding Image position by construction ????
