light ✅

• optics is the study of light
• we can only see objects around us if light enters our eyes which is reflected
• our eyes receiver physical stimuli in the form of light energy and sends those stimuli as electrical signals to the brain, these signals are then interpreted as images which can be luminous and non-luminous
• luminous objects are things that can be seen because they give out their own light
• such luminous objects can be lamps, fire, Sun, stars and glow sticks
• non-luminous objects are things that can be seen because they reflect light from a light sources into our eyes
• such non-luminous objects are pictures on the wall, clothes, most objects
• light travels in a straight line
• a beam of light is possible by light scattering from dust particles and the edges of these beams are straight, proof that light travels in a straight line
• the visible light spectrum is the segment of the electromagnetic spectrum that the human eye can view

  
• in air, light travels at a speed of 3 x 10^8 m/s
• the straight paths of light are known as rays
• a beam is a bundle of rays
• use of ray models to help represent the path taken by light to explain our observations how light behaves, with arrows in the models to indicate direction
• divergent rays are rays that spread out from a point
• parallel rays are rays that lie on the same line or same direction and will never meet
• convergent rays are rays that will meet from a point
• Properties of light: 

  • • a form of energy
  • • travels in straight lines 
  • • travels at a speed of 3 x 10^8 m/s in a vacuum 
  • • consists of 7 main colours 
  • • reflected, refracted and dispersed 
• transparent objects allow light to pass through easily e.g. clear glass
• translucent objects are objects which only some light rays can pass through, but not at all e.g. frosted glass
• opaque objects are objects that light is unable to pass through e.g. wooden block
• reflection of light allows us to see non-luminous objects
• • when surface of a flat piece of glass is coated with silver, almost of the light falling on the opposite surface is reflected 
• • mirrors are employed in many instruments (galvanometers, sextant, cameras, periscopes) 
• reflection is the rebounding of light at a surface (usually reflected by a mirror )
• the laws of reflection is: a) the incident, the reflected and normal ray at the point of incidence all lie in the same plane 

  b) angle of incidence = angle of reflection
• when light strikes a surface, it will rebound
• incident ray is when the light ray hits the reflecting surface
• the angle of incidence is the angle between the incident ray and the normal ray
• the point of incidence is the point at which incident rays hits the surface
• the normal is perpendicular to the reflecting surface at the point of incidence
• the reflected ray is when the light ray changes direction after hitting the reflecting surface
• the angle of reflection is the angle between the reflected ray and normal
• all surfaces reflect light
• different surfaces will cause different types of reflection
• is the surface is smooth, there will be regular reflection
• if the surface is rough, there will be diffused reflection
• regular reflection: -occurs on a smooth surface (e.g mirror) 

  -angle of incidence = angle of reflection

  -all rays have the same angle of incidence and angle of reflection 

  -parallel incident rays are reflected in the same direction as surface is even 
• diffuse reflection: -occurs at rough surfaces (e.g sandpaper, cloth) 

  -angle of incidence = angle of reflection for each ray 

  -angle of incidence for each ray is different as surface is uneven 

  -reflected rays go in diff directions 
• characteristics formed by plane mirrors:

  • virtual (image cannot be formed on a screen) 
  • • upright
  • • image distance = object distance 
  • • same size as object 
  • • laterally inverted