P14

• Reflection from a smooth surface is called specular reflection
• Reflection from a rough surface is called diffuse reflection
• In specular reflection, the parallel rays of light are reflected in single direction
• In diffuse reflection the parallel rays of light are reflected in different directions.
• angle of incidence is angle between the incident ray and normal
• angle of reflection is angle between reflected ray and normal
• Image from a mirror is virtual, upright, same size as object and same distance behind mirror as object infront
• Virtual image is formed where light rays appear to come from.
• When light rays travel from a less dense medium into more dense medium, e.g. air to glass, the ray is refracted towards normal
• When light rays travel from a more dense medium into less dense medium, e.g. glass to air, the ray is refracted away from normal
• From more dense medium to less dense medium, the angle of refraction is greater than the angle of incidence
• From less dense medium to more dense medium, the angle of refraction is less than the angle of incidence
• Human eye sees different frequencies of light as different colours
• White light is made up of all colours
• A white surface has no pigments so it reflects light of any wavelength either partially ro totally
• A black surface absorbs all wavelengths and reflects none
• Colour filters absorb certain wavelengths and transmit others.
• Transparent objects transmit all light incident on them, no light is absorbed at the surface
• Translucent objects allow light to pass through but are scattered or refracted inside of them
• Opaque objects will absorb all light incide on them
• An object will appear white if all wavelengths are reflected equally
• An object will appear black if all wavelengths are absorbed
• An object will appear transparent if all light is transmitted and only small amount is reflected or absorbed
• A camera uses a converging lens to form a real image of an object
• A magnifying glass uses a convex lens to produce a virtual, magnified image
• In visible light, red has the lowest frequency and violet has the highest frequency.
• when an object is placed closer to convex lens than focal point, the lens forms virtual, upright and magnified image on same side of lens as object
• refraction is the change in direction of any kind of wave as it changes speed at boundary
• image produced by diverging lens is always virtual
• the distance from centre of lens to principal focus is called focal length
• there is principal focus on either side of lens as light can pass thru lens in either direction
• parallel rays of light pass through a converging lens are refracted so that they converge to focal point
• if object is further away from the lens than 2F, an inverted real image is formed that is smaller than object
• if object is on 2F, an inverted real image that is same size is formed
• if obect is closer to lens than focal point an inverted real image is formed behind object so image is magnified