Listed in order of use:
The anatomy and function of the human eye:

http://www.tedmontgomery.com/the_eye/
http://www.virtualmedicalcentre.com/uploads/VMC/DiseaseImages/2133_eye_anatomy_label_v2_700.jpg
http://www.macula.org/anatomy/
http://www.emedicinehealth.com/anatomy_of_the_eye/article_em.htm
http://www.eyes.com/eye-anatomy-cornea.html
http://www.lensshopper.com/eye-anatomy.asp

the limited range of wavelengths of the electromagnetic spectrum

http://www.geo.mtu.edu/rs/back/spectrum/
http://www.purchon.com/physics/electromagnetic.htm
http://en.academic.ru/dic.nsf/enwiki/8118003
http://wc.pima.edu/Bfiero/tucsonecology/animals/Images/rw_pitorgan.jpg
http://web1.stmaryssen-h.schools.nsw.edu.au/SMSHS/ricks%20sites/Biology%20web%20site/HSC_9_5%20communications/Bee%20eye%20folder/bee_eye.html
http://www.animations.physics.unsw.edu.au/jw/EMspectrum.html
http://www.enotes.com/forensic-science/electromagnetic-spectrum

Refraction of light

https://chemicalparadigms.wikispaces.com/file/view/65018453.JPG/33790803/65018453.JPG
http://zonalandeducation.com/mstm/physics/light/rayOptics/refraction/refraction1.html
http://www.excimer.sk/images/excimer/emmetropie.jpg
http://www.tutorvista.com/content/science/science-ii/human-eye-colourful-world/power-accommodation.php
http://www.youtube.com/watch#!v=15P8q35vNHw&feature=related
http://www.aoa.org/myopia.xml
http://www.allaboutvision.com/conditions/myopia.htm
http://www.allaboutvision.com/conditions/hyperopia.htm
http://www.aoa.org/x4696.xml

Photoreceptor cells
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1941804/pdf/zpq13158.pdf
http://hyperphysics.phy-astr.gsu.edu/hbase/vision/rodcone.html
http://www.chm.bris.ac.uk/webprojects2003/rogers/998/Rhoeye.htm
http://www.spiritus-temporis.com/photopsin/
http://www.reference.com/browse/photopsin
http://www.betterhealth.vic.gov.au/bhcv2/bhcarticles.nsf/pages/Colour_blindness
http://www.youtube.com/watch?v=Wj8xZuC7nyM&feature=fvsr

Sound
http://www.youtube.com/watch?v=s9GBf8y0lY0
http://home.comcast.net/~wnor/lesson11.htm

The ear
http://www.helium.com/items/1352824-structure-of-the-human-ear
http://www.mydr.com.au/hearing-health/ear-anatomy
http://www.enchantedlearning.com/subjects/anatomy/ear/
http://www.youtube.com/watch?v=nTXk2nQMQ5g
http://www.medicinenet.com/eustachian_tube_problems/article.htm
http://www.youtube.com/watch#!v=bwQdTctM9eU&feature=related
http://media-2.web.britannica.com/eb-media/00/14300-004-5FF07709.gif
http://hyperphysics.phy-astr.gsu.edu/hbase/sound/corti.html