Physiocs Bio 134
GEOMETRICAL OPTICS
Behaviour of light due to diffraction and interference
Ray model of light (cascade of photos)
- Light can be seen through it being a source, reflected, transmitted, or absorbed
o Nature of material and surfaces determines the amount of absorption,
reflection, and transmissions (colour is determined by the brain when
receiving the reflected wavelengths)
- Wavefront: set of points of equal phase – point where the wave disturbance is
maximum/point where wave disturbance is 0
- Ray: points in direction of propagation of a wave and is perpendicular to the wavefronts
- Huygens principle: each point on a wavefront is a source to secondary
wavelets/disturbances
- Lens: stretches or compresses and bends light (mailable – contract/compress)
o Denser than cornea = bends light more/slows down light
- Cornea: transparent layer
o Refractive index (n): how severally light bends
- Iris: membrane opening pupil to let light through and gives colour
- Retina: optical senses (light senses) that is sensitive to light/stimuli
o Rods: sensitive to light and dark
o Cones: colour
- Optic nerve: transfers stimuli to impulse (electric signals)
- Vitreous humour: lowest refractive index (like water)
- Gravitational lensing: light bends when going through big masses
- Changing refractive index and position of object affects the image
- Light propagates in straight lines which is called a light ray:
o Shadows
o Laser light
- Light ray properties:
o Reflection and refraction
o Image formation by mirrors and lenses
- Eye/brain perceives that the object lies on the dotted line (line of sight)
- Smooth surface reflection/specular reflection (optical instruments): incident rays all
reflect at same angle
- Rough/irregular surface reflection/diffuse reflection (everyday): angles of reflection for
incident rays are = angles of reflected rays but normal is at
random angles so reflected rays travel in many directions (scatter)
REFLECTION
Plane mirrors
- Angle of incidence: angle between the incident ray and the normal
(line perpendicular to the surface where the ray touches the surface) - θ i
, Physiocs Bio 134
- Angle of reflection: angle between reflected ray and normal - θ r
- Incident ray always reflects on the other side of the normal to form the reflected ray
- Image in front of mirror (object) is just as deep as the virtual image
Law of Reflection
1. Reflected ray lies in the same plane as the incident ray and the normal to the surface
at the point of incidence (plane of incidence). The 2 rays are on opposite sides of the
normal
2. Angle of incidence = angle of reflection (θ i = θ r)
Terminology
- Upright = positive height and flipped = negative height
- i and o has the same value
- Image is the apparent depth
- Inverted means upside down
- Real means it’s on the left not in line of sight
- Virtual image: trace light rays back to point which they
appear to diverge even if they don’t come from that point
- Real image: light rays pass through the image point
o Viewer located beyond the image so that the rays from a point on the object
all diverge from a point on the image (intersection = image)
- All images formed by a plane mirror are:
o Virtual (rays appear to orginate at the image bheind the mirror, no rays go
trhough the mirror)
o Upright but inverted from left to right
o As far behind the mirror as the object is in front = -d i = do
o Just as large as object -hi = ho
Negative as it is on the virtual image side
- Principles for drawing ray diagrams for concave mirrors:
o Ray parallel to the axis and then reflected through the focal point
o A ray along the radius is reflected back on itself
o A ray along the direction through the focal point to the mirror is reflected
parallel to the axis but below
o Ray incident on the vertex of the mirror at O reflects at an equal angle to axis
- Principles for drawing ray diagrams for convex mirrors:
o Ray prallel to the principle axis is reflected as if it came from a focal point
o A ray along a radium is reflected back on itself (C)
o A ray directed towards the focal point is reflected prallel to the principle axis
GEOMETRICAL OPTICS
Behaviour of light due to diffraction and interference
Ray model of light (cascade of photos)
- Light can be seen through it being a source, reflected, transmitted, or absorbed
o Nature of material and surfaces determines the amount of absorption,
reflection, and transmissions (colour is determined by the brain when
receiving the reflected wavelengths)
- Wavefront: set of points of equal phase – point where the wave disturbance is
maximum/point where wave disturbance is 0
- Ray: points in direction of propagation of a wave and is perpendicular to the wavefronts
- Huygens principle: each point on a wavefront is a source to secondary
wavelets/disturbances
- Lens: stretches or compresses and bends light (mailable – contract/compress)
o Denser than cornea = bends light more/slows down light
- Cornea: transparent layer
o Refractive index (n): how severally light bends
- Iris: membrane opening pupil to let light through and gives colour
- Retina: optical senses (light senses) that is sensitive to light/stimuli
o Rods: sensitive to light and dark
o Cones: colour
- Optic nerve: transfers stimuli to impulse (electric signals)
- Vitreous humour: lowest refractive index (like water)
- Gravitational lensing: light bends when going through big masses
- Changing refractive index and position of object affects the image
- Light propagates in straight lines which is called a light ray:
o Shadows
o Laser light
- Light ray properties:
o Reflection and refraction
o Image formation by mirrors and lenses
- Eye/brain perceives that the object lies on the dotted line (line of sight)
- Smooth surface reflection/specular reflection (optical instruments): incident rays all
reflect at same angle
- Rough/irregular surface reflection/diffuse reflection (everyday): angles of reflection for
incident rays are = angles of reflected rays but normal is at
random angles so reflected rays travel in many directions (scatter)
REFLECTION
Plane mirrors
- Angle of incidence: angle between the incident ray and the normal
(line perpendicular to the surface where the ray touches the surface) - θ i
, Physiocs Bio 134
- Angle of reflection: angle between reflected ray and normal - θ r
- Incident ray always reflects on the other side of the normal to form the reflected ray
- Image in front of mirror (object) is just as deep as the virtual image
Law of Reflection
1. Reflected ray lies in the same plane as the incident ray and the normal to the surface
at the point of incidence (plane of incidence). The 2 rays are on opposite sides of the
normal
2. Angle of incidence = angle of reflection (θ i = θ r)
Terminology
- Upright = positive height and flipped = negative height
- i and o has the same value
- Image is the apparent depth
- Inverted means upside down
- Real means it’s on the left not in line of sight
- Virtual image: trace light rays back to point which they
appear to diverge even if they don’t come from that point
- Real image: light rays pass through the image point
o Viewer located beyond the image so that the rays from a point on the object
all diverge from a point on the image (intersection = image)
- All images formed by a plane mirror are:
o Virtual (rays appear to orginate at the image bheind the mirror, no rays go
trhough the mirror)
o Upright but inverted from left to right
o As far behind the mirror as the object is in front = -d i = do
o Just as large as object -hi = ho
Negative as it is on the virtual image side
- Principles for drawing ray diagrams for concave mirrors:
o Ray parallel to the axis and then reflected through the focal point
o A ray along the radius is reflected back on itself
o A ray along the direction through the focal point to the mirror is reflected
parallel to the axis but below
o Ray incident on the vertex of the mirror at O reflects at an equal angle to axis
- Principles for drawing ray diagrams for convex mirrors:
o Ray prallel to the principle axis is reflected as if it came from a focal point
o A ray along a radium is reflected back on itself (C)
o A ray directed towards the focal point is reflected prallel to the principle axis
