Waves and light AS 2.3

DEMONSTRATE UNDERSTANDING OF WAVES AS 2.3Light 4 weekswaves 4 weeksLight infoLenses/mirrorsConcave/convex/planeReflection/refractionIncident/reflected raysRay diagrams how to draw and components neededLaws of reflectionLIGHTType of electromagnetic radiation Oscillating electric and magnetic fieldsTravel together at a speed of 3.0x 108 ms (speed of light)Form of energyAppears to travel in straight lines

A lens is an optical device with perfect or approximate axial symmetry which transmits and refracts (bends) light, converging or diverging the beam.

A mirror is an object with at least one reflective surface. A plane mirror has a flat surface. Curved mirrors are also used, to produce magnified or diminished images or focus light

Concave: curves inwards

Convex: curves outwards

Plane:flat surface

Rays and wave fronts can generally be used to represent light when the light is interacting with objects. We will mainly use rays to analyse how light interacts with mirrors and lenses.

ReflectionReflection from a mirror:Incident rayNormalReflected rayAngle of incidenceAngle of reflectionMirrorIncident and reflected rays.......The ray of light approaching the mirror is known as the incident rayThe ray of light that leaves the mirror is known as the reflected rayAt the point of incidence where the ray strikes the mirror, a line can be drawn perpendicular to the surface of the mirror. This line is known as a normal line The normal line divides the angle between the incident ray and the reflected ray into two equal angles. The angle between the incident ray and the normal is known as the angle of incidence. The angle between the reflected ray and the normal is known as the angle of reflection.Laws of reflection.....

Ray diagramsAre diagrams drawn to scale and used to determine the details of an image produced by either a lens or mirror

You need to know how to figure out the following details of the image produced

Position: how far along the principal axis, may be either behind or in front of the mirrorSize: cm/heightNature: upright/inverted, virtual or real, magnified or diminishedFocal point: the point through which all parallel light rays are reflected throughCentre of curvature: centre point circleRadius of curvature: distance between pole and centre of curvature (same as radius of circle)The focal length of a curved mirror is half the radius of curvature

A mirror is drawn as a curved line and/or a straight mirror line to make ray diagrams easier. Dashed lines or shading on the non-reflective side.

Draw a ray diagram of:A concave mirror, with principal axis, focal point of 4cm and centre of curvature of 8cm.Draw an object (arrow) of 2cm height 5cm from the pole.

1. Look at the diagram below. Which one of the angles (A, B, C, or D) is the angle of incidence? ______ Which one of the angles is the angle of reflection? ______

2. A ray of light is incident towards a plane mirror at an angle of 30-degrees with the mirror surface. What will be the angle of reflection?

3. A ray of light is approaching a set of three mirrors as shown in the diagram. The light ray is approaching the first mirror at an angle of 45-degrees with the mirror surface. Trace the path of the light ray as it bounces off the mirror. Continue tracing the ray until it finally exits from the mirror system. How many times will the ray reflect before it finally exits?

4. You can observe the image of the sun in the windows of distant buildings near the time that the sun is rising or setting. However, the image of the sun is not seen in the windows of distant building during midday. Use the diagram below to explain.

Formula........ : is the image distance

: is the object distance

Magnification factor:

ConvergingDivergingConcaveConvexFocal lengthf>0+ve focal lengthf1 magnified