• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

The Resolving Power Of The Eye

Extracts from this document...

Introduction

The Resolving Power Of The Eye

Objective

        By using the resolving power of the eye find the separation between two cones on the retina.

Introduction

        The resolving power of the eye is the angle created when the separation of two objects is the least distance where the two objects can still be seen.

        To find the theoretical resolving power of the eye the formula:

θ= 1.22λ

      D

Is used where         θ= The resolving power of the eye

λ= The wavelength of the light used

D = The diameter of the pupil

And 1.22 is a constant

        This formula gives the theoretical value of θbecause the receiving of the light is not a continuous process. The retina has numerous individual receptors and for two objects to be resolved then two cones must be stimulated either side of ad un-stimulated cone.

To resolve two objects the central maxima of the first object must be no closer than the first minima of the second object as above.

Plan

Prime Factors

        To calculate the resolving power of the eye one must first consider the factors that have bearing upon the experiment. The greatest factor is the

...read more.

Middle

        In total darkness with the LED turned on behind the card stand or kneel so that the two apertures are at eye level. From close to the card work gradually backwards until the two lights can only just be defined and appear separate. Mark this point on the floor for measuring later when in full light. Continue this process changing the holes used for the different readings on different separations. Repeat the whole experiment three times.

Safety

        Safety is not enforced strongly as the experiment has few dangerous elements. However, it is common sense to stay safe by not putting electrical equipment next to or in a sink in use as is not running around in the darkened lab.

Calculations

        To calculate the theoretical value; θ, of the resolving power of the eye use the wavelength of the light by the LED and the measured diameter of the pupil. This will give a reference value for the calculated resolving power; this can be used to check х, as х cannot exceed θ.Х, the actual resolving power, can be calculated, in radians, by using separation of the apertures and the distance between the eye and apertures. By rearranging s = dx you get x = s/d.

...read more.

Conclusion

        My final result for the separation of the two cones, 3.15 x 10-6m ± 2.65% was a factor of 10 out from the literature value of 50μm. This could be caused by an error in calculation, measurement or inaccuracy caused by the number of assumptions that I used.

        The final result for the separation of two cones on the retina is dependant upon the diameter of the eye as a 10mm difference in this could double or half the answer, for the theoretical value of θ the pupil diameter is the most important factor.

        The techniques I used were suitable for this experiment but could have been vastly improved, the conclusions drawn, mainly the cone separation, were very reliable as for such a small distance a factor of ten out is very accurate. A large number of errors and inaccuracies can be eliminated from the experiment. Random errors can be removed completely and systematic errors reduced. By carrying out the experiment in fully darkened conditions with no light source at all, time of day and conditions outside will have no effect. Also by performing the experiment in one afternoon after acclimatizing (sitting in the dark) the pupil diameter will be as large as possible and constant plus any tiredness should be alleviated.

...read more.

This student written piece of work is one of many that can be found in our AS and A Level Electrical & Thermal Physics section.

Found what you're looking for?

  • Start learning 29% faster today
  • 150,000+ documents available
  • Just £6.99 a month

Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

See related essaysSee related essays

Related AS and A Level Electrical & Thermal Physics essays

  1. Using an LDR to detect the intensity of plane polarised light allowed through a ...

    * Slower response times, but this is negligible due to there being no sudden changes Photodiode * Can be photovoltaic or photoconductive, giving greater flexibility * React negligibly to ambient light * Can be used with many different frequencies of light based on material of the window * Very fast

  2. Choosing a light source

    were close but not close enough like natural light. TASK 3: In this task I am going to research how a spectrometer and a diffraction grating can be used to determine the wavelength of light sources. This is a spectrometer The sorts of reads you need to take or have are: 1. sin ? (which represents the angle i.e.

  1. Investigating the monitoring systems used on modern day large A/C for detection of specific ...

    From the diagram on the opposite page, the pick - up unit is a linear - velocity detector that converts the mechanical energy of vibration into an electrical signal of proportional magnitudes. It does this by means of a spring-supported permanent magnet suspended in a coil attached to the interior of the case.

  2. I aim to find out how distance affects the light intensity emitted from an ...

    To measure the current I would put the ammeter in series with the LDR and with a 9V power pack. Then I would record the results from different light intensities. If another resistor is put into the circuit in series to the LDR then a potential divider can be made this should give a better reading than the resistance alone.

  1. Build a successful sensor that will measure the proximity of a light source.

    If the resistance or conductance changes the current and voltage will also change.' As you increase the resistance of a resistor the current and voltage across the resister will decrease. This law is proven especially well by a potentiometer, (or a variable resister).

  2. How does changing the distance from a light source affect the power output of ...

    The effect is that current flows through the junction. Photovoltaic cells can only absorb about 15 % of the sunlight's energy because they can only absorb photons, which come from visible light. A lot of the sunlight's energy is in other electromagnetic waves such as Ultra violet, or infrared.

  1. Intensity on the power output of a solar cell.

    This is the opposite of N-type in that there is an extra 'hole' for an electron. When these two parts of the silicon are put together, the extra negative electrons rush to fill up the positive holes. However instead of filling the holes, they mix and form a barrier at the junction between the two types of silicon.

  2. Light intensity

    During the preliminary practical, there are many things I can do to get the optimum results. That includes keeping the distance and height the same, but also taking the correct resistance reading. You can set the resistance readings on the Multimeter to different levels of accuracy.

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work