Light Chapter 46
Light • Light is a form of energy. • Light can do work i.e a solar panel or Crooke’s radiometer. (Light energy can be converted to other forms of energy)
Light • Luminous objects are a source of light. i.e. The Sun • Non-Luminous objects do not give of their own light. • Non-Luminous objects can be seen because light reflects off them.
Luminous vs Non-Luminous Luminous Non-Luminous
Light • Light travels in straight lines. • If one piece of card is moved the light can no longer be seen
Light • Shadows are formed because light travels in straight lines.
White Light • White Light is a mixture of 7 different colours called a spectrum.
White Light • The breaking up of white light is called dispersion. • White light can be dispersed using a triangular glass block called a prism.
Reflection • Reflection – Light bounces back off surfaces. • Light reflects in a regular manner off smooth, shiny, polished surfaces.
Reflection The N is called the normal and is perpendicular to the mirror. Angle A = Angle B
A Periscope • A periscope can be used to look around obstacles. • The mirrors are positioned in the periscope at a 45o angle.
Refraction • Refraction is the bending of light as it passes from one medium to another. • Note the light ray gets pulled towards the denser substance. • Eg Swimming pool.
A Lens • A lens is a piece of glass with a curved surface which is used to bend or refract light.
Concave • A concave lens spreads out the rays of light. • Diverging lens
Convex • A convex lens bends the rays of light together to a point. • Converging lens
Uses of Lenses • Concave: • Used in glasses to correct short sighted eyes. • Convex: • Glasses to correct long sighted eyes. • Magnifying glasses. • Telescopes • Cameras • Microscopes