IB Sl Physics Sight and Waves Flippingphysics by Nothingnerdy
presentsa productionSight and Wave Phenomena 1
Inside the eyeLearn the labellingVitreous humour of the eye Aqueous humour Optic nerve Fovea Retina Blind spot Lens Pupil Cornea Iris 2 Ciliary muscle
Inside the eye Learn the functions of the eye partsAqueous humour Retina Fovea Lens Optic nervePupilCornea Iris Blind spot Ciliary muscle Vitreous humour 3
AccommodationHow the ciliary muscles shape the lens to focus light Near point The closest distance that an eye can focus. Conventionally, this is 25 cm. Far point The furthest distance that an eye can focus (ciliary muscles relaxed). Conventionally, 4 this is at inﬁnity.
Depth of vision Depth of vision refers to the ability to see things in three dimensions and thus to judge distance. The different cues we use to see 3D are: Relative sizes of objects;perspective; parallax; binocular vision (using two eyes) 5
Rods and cones Two types of receptor cell in the retina Cones: detect colour and visual acuity (sharpness). There are three types of cone which are sensitive to different wavelengths of light. Red (long λ, 560 nm)Rods: detect movement and low Green (medium, 530 nm)light intensity. Very sensitive to Blue (short, 430 nm) light but not colour. 6
Retina The graph shows that cones are concentrated at the fovea where there are no rods. The rods are spread more evenly. Photopic vision = Scotopic vision = nocolour under normal colour, dim light ie thelighting ie the cones 7 rods
Colour blindness The commonest form is red-green, which is caused by problems in the cones. It is genetically inerited, usually by males. The Ishihara test is used to identify colour- blindness. This is a simulation of how people see the top left image. Deuteranomaly is the most common due to a mutation in 8 the green pigment.
RedGreenBlue The continuous spectrum of visible light can be reduced for sense perception purposes to three Primary colours: Red, Green and Blue (R, B, G).Red light contains only R and no B or GRed objects reﬂect only R and absorb B and GRed ﬁlters transmit only R and absorb B and G 9