A Global Science Community | Home page Medical Animation Library ©Copyright 2009 A.D.A.M., Inc. Any duplication or distribution of the information contained herein is strictly prohibited. The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed physician should be consulted for diagnosis and treatment of any and all medical conditions. Hearing Test - Can You Hear This? We got a lot of positive feedback on our Can You Hear Like a Teenager? article, and it inspired us to take it just a little bit further. Check your hearing with a list of tones that go from 8Hz all the way up to 22,000Hz. It’s fairly common for people who are over 25 years of age to not be able to hear above 15kHz and also experience some level of hearing loss or hearing damage such as tinnitus. Musicians have a much higher risk of hearing loss that most people do, and many of us don’t really wear proper hearing protection. Take our online hearing test: listen to each of these tones and let us know where your hearing cuts out. Importance of Hearing Protection If you’re around loud music a lot like I am, or if you are experiencing some hearing loss, I highly recommend getting a pair of hearing protection earplugs. The Etymotic earlplugs don’t muffle the sound like conventional earplugs – they basically give you the same frequency response as without, but with a bit lower volume.
Eye:optics, anatomy and accommodation: Physclips - Light The photoreceptor cells in the human retina are classified, by their shape, into rods and cones. Cones, which are responsible for colour vision, come in three types, called red, green and blue according to whether they respond most strongly to long, medium and short wavelengths. (Page on this still to come.) Cones are concentrated in the fovea, the area directly behind the pupil, while rods are distributed over the whole retina. The photoreceptors are connected to retinal ganglion cells, which transmit electrical pulses called action potentials through the optic nerve to the brain. In this sketch, light arrives from the left, which means that light travels through the nerves on its way to the photo receptors.