chapter 5 - light

made by dillon tan 2bn

light

form of energy that enables us to see things around us when it enters our eyes

shadow

a dark area where light from a light source is blocked by an opaque object

umbra

innermost and darkest part of a shadow, where light is completely blocked by the obstructing body

penumbra

the region in which only a portion of the light source is obscured by the obstructing body

incident ray

light ray hitting the reflecting surface

reflected ray

light ray travelling away from the reflected surface

angle of incidence

angle between the incident ray and the normal

angle of reflection

angle between the reflected ray and the normal

normal

line perpendicular to the surface at the point of incidence

1st law of reflection

angle of incidence is equal to the angle of reflection

2nd law of reflection

the incident ray, reflected ray and normal, at the point of incidence, lie on the same plane

how to draw ray diagram

1. locate the position of the image

2. draw 2 rays from the image straight to the eye

3. draw the incident rays from the object

virtual image vs real image

formed by extension rays vs formed by converging rays

cannot be projected on a screen vs can be projected on a screen

upright vs inverted

characteristics of an image formed by a plane mirror

upright, same size as object, object distance from mirror equal to image distance from mirror, laterally inverted, virtual

virtual

convex

smaller image

concave

magnified image

refraction

change in direction of a light ray as it travels from a medium to another of a different optical density, due to a change in the speed of light in the medium

less dense to denser medium

speed of light is slower so light ray bends towards normal

denser to less dense medium

speed of light is faster so light ray bends away from normal

angle of incidence is zero

light ray will travel without any deviation from its original path

refractive index

speed of light in vacuum : speed of light in medium

effect of refraction

causes object to appear nearer to surface of water

dispersion of light

white light is split into its component colours

colour bends most - least

violet, indigo, blue, green, yellow, orange, red

BGR CYM

blue green red, cyan yellow magenta

how to see colour of an object under a specific colour of light

we can see the colour of object when the light falling on it contains the same colour of the object