PASCO Eye Lab
The Eye Lab studies the optics of the human eye and how images are formed on the retina of the eye.
Experimental Steps
Part 1: Images Formed in the Eye
The image on the retina was inverted, but we see things right side up because our brain flips the image. If you wrote something on a piece of paper and held it upside down in front of the eye, on the retina it would be right side up, but our brain inverts the image, so we would percieve the image as upside down.
Part 2: Accommodation
Accommodation is accomplished by muscles that change the curvature of the crystalline lens in the human eye. The curvature of the crystalline lens increases to accommodate a nearby object.
Part 3: Far-sightedness (Hypermetropia)
A person with far-sightedness needs a converging lens to move the image closer to the eye's lens system (converging would make light bend more). A hypermetropic eye has a near point that is too far. The distance between the eye and the image is greater than the distance between the eye and the object. You can't see up close, so the image needs to be pushed back to be able to see it.
Part 4: Near-sightedness (Myopia)
A person with near-sightedness needs a diverging lens to move the image further away (concave/ diverging lens would help the light bend less). A near- sighted eye has a far point that is too near. The distance between the eye and the image formed by the glasses would be less than the distance between the eye and the object.
Part 5: Astigmatism
Since the lens surfaces of a normal eye are spherical, the lens surfaces of someone who has astigmatism are not rotationally symmetrical. To fix this, a cylindrical lens needs to be used to cancel out the error of the eye's lens.
Part 6: Blind Spot
Cover one eye, hold the template at arm's length, and focus on one of the shapes (the cross). While maintaining focus, you slowly move the template closer until the other shape (the dot) disappears from view. This disappearance indicates the dot has fallen on your eye's blind spot, which is the area where the optic nerve connects to the retina. The right eye can see the left eye's blindspot and vice versa.
Part 7: Apparent Size
When you look at something, its apparent size is determined by the size of the image formed on your retina, which depends on both the size of the thing and its distance from your eye.
Optics Experimental Review
What did we learn?
The PASCO Eye Lab demonstrates how light is refracted through lenses to form clear images, similar to how the human eye focuses light on the retina. It helps explain key optical concepts like focal length, image formation, and refraction, while also showing how vision problems such as nearsightedness and farsightedness occur and how corrective lenses adjust the focus to produce a clear image.