Human Eye Resolution | Te Kokinga o te Māhea o Ngā Whatu
The angular resolution of the human eye is measured in a series of experiments: an easy to construct, astronomy-related demonstration/activity that illustrates the angular resolution of the human eye, colour sensitivity, and angular magnification.
Angular resolution of the human eye, angular magnification, colour sensitivity.
Te Reo Māori Version
Tape several layers of waxed paper to the front of an ordinary torch to reduce the brightness of the light and to create a more diffuse source. Put two pinholes into a piece of aluminium foil 3 mm apart and tape this over the waxed paper. Place the torch at the front of a darkened room at eye height and measure the distance at which you can just distinguish two sources. The angular resolution of the eye can be calculated as:
You will need a room at least 7 m in length. Results vary from person to person but agree, within an order of magnitude, with the accepted figure of around 0.3 milliradian to 1 mrad (0.02° to 0.05°). Age, health and the state of a person’s eyesight will affect the results, as will the environment, light or dark, background contrast, etc. Changing the number of layers of wax paper can be used to investigate the effect of brightness upon the angular resolution. The central fovea has a dense accumulation of cones sensitive to red and green light. Try using red and green cellophane under the foil, one over each hole, to see if the ability to resolve the holes is improved.
Repeating the test with a pair of binoculars or a telescope (though a greater distance will be required) can be used to test the magnification of the binoculars or telescope. The magnification can be calculated as the ratio of distance measured with the telescope to the distance measured with the unaided eye. Compare this with the stated magnification on the telescope. Another version of the apparatus that we sometimes use involves a red LED and a green LED.
Individual teachers are responsible for safety in their own classes. Even familiar demonstrations should be practised and safety-checked by individual teachers before they are used in a classroom.
Notes, Applications, and Further Reading
You can find some useful discussion of human vision on the Hyperphysics web site among many others.
This teaching resource was developed by the Te Reo Māori Physics Project with support from
- Te Puni Kōkiri
- The MacDiarmid Institute
- Faculty of Science, Victoria University of Wellington
- School of Chemical and Physical Sciences, Victoria University of Wellington
- The New Zealand map shown on the poster frame above is used with permission from www.nz.com.
- We are grateful to Dr. Robert Jacobs, Associate Professor of Optometry at The Department of Optometry and Vision Science at Auckland University , for a number of useful conversations and suggestions.
- The human eye cone response graphic was adapted from one provided by Hyperphysics.
- The astronomical photos are from www.starrynightphotos.com.
- This resource was filmed partly at Te Herenga Waka Marae.