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

Aim of the Laboratory Experiment: Understanding of propagation of light waves phenomena by using a photometer device.

Extracts from this document...

Introduction

Alexander 11 IB C

11.04.2012

Teacher: Plamen Malinov

Investigating Propagation of Light Waves

Lab Report № 13

Aim of the Laboratory Experiment: Understanding of propagation of light waves phenomena by using a photometer device.

Hypothesis: The luminous intensity of a lamp will increase as the voltage increases. However, when the distance between two lamps decreases, the voltage will also decrease, and as a result of this I predict that the light intensity will also decrease.

General Background: Light consists of electromagnetic waves with wavelength in vacuum from 400 to 700 nm. From a point source light propagates in every direction. The light intensity of a source I is measured by the international unit called candela (cd). The illumination E of a unit surface (1 m2) is measured by unit called lux (lx). E is connected with the light intensity of the source and its distance r by the law of Lambert. The law of Lambert states: E = (I / r2) cos α, where I is the light source intensity, r is the distance to the source, E is the illumination of a surface with area of 1 m2, and αis the angle between the distance to the source and the normal (imaginary line perpendicular to the surface).

A photometer is a device which consists of two surfaces which are illuminated by two different light sources. A photometer is illustrated in this picture:  

image00.jpg

Both surfaces are at the same angle α in respect to their light source.

...read more.

Middle

14.8

14.7

14.8

14.8

± 0.1

Residuals r2

0

0.1

0

2

20

22

19

21

20.7

± 1.7

Residuals r2

1.3

1.7

0.3

3

25

25.5

24.0

26.5

25.3

± 1.3

Residuals r2

0.2

1.3

1.2

The error for the distance = one quarter of the cm or 0.25 cm

Table 1: Experimentally checking the photometer

The average (mean) value of the distance r2 can be calculated when the total result from the three measurements is divided by 3.

Table 2: Determining the light intensity of an unknown light source

No

r1, cm

First measurement r2, cm ± 0.25 cm

Second measurement r2, cm ± 0.25 cm

Third measurement r2, cm ± 0.25 cm

Average r2, cm

Experimental error ∆r2, cm

1

15

13.5

13.7

14.0

13.7

± 0.3

Residuals r2

0.2

0

0.3

2

20

17.2

19.6

18.2

18.3

± 1.3

Residuals r2

1.1

1.3

0.1

3

25

19.6

20.7

19.8

20.0

± 0.7

Residuals r2

0.4

0.7

0.2

The light intensity of the second lamp for the first measurement of the 2nd task is:

I2 = I1 (r22 / r12), where r2 is the average distance.

I2 = 25 x (13.72 / 152) = 20.9 cd

The light intensity of the second lamp for the second measurement is:

I2 = 25 x (18.32 / 202) = 20.9 cd

...read more.

Conclusion

Evaluation

It was difficult for the team to set the light intensity  I1 andI2 to be exactly the same for the two sources because we did not have more precise device than our eyes, which resulted in a small inaccuracy. The sunlight entering through the windows of the laboratory was creating troubles for the team to see only the luminous light. It is evident on my picture that the photometer used is old and it used to confuse us when we were setting the light intensity I1 andI2 to be equal. An old and a poor calibrated instrument increases the systematic errors, thus increasing the experimental error.

Improvements

The experiment can be improved when it is being held in a darker room, with limited or no presence of sunlight, because in this way human eyes will be more sensitive to the differences in the light intensity and would determine the equal light intensity of the sources more accurately and precisely. The photometer can be replaced with a newer and better one, a digital photometer if possible that would measure the equal light intensity electronically like this photometer:  image02.png

...read more.

This student written piece of work is one of many that can be found in our International Baccalaureate 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 International Baccalaureate Physics essays

  1. Physics Lab Report. Aim: To find out how a light dependent resistor is affected ...

    Note down the reading for the light intensity from the logger pro software and also note down the reading of the current and the voltage. 5. Move the light bulb away from both the resistor and the light sensor but such that the light sensor and the resistor are equally apart from the filament light bulb.

  2. Investigating the Breaking Distance of a Cart

    The values on the graph do not begin from 0 on both axes but with the appropriate values. If the lowest uncertainties were taken into account a line passing through zero would be possibly visible. The line of best fit does pass through most of the error bars on each value.

  1. design of a variable resistor

    3. There is not any pattern. I only found out that the difference in average resistance between mm and mm is 0.002031997, and the difference in average resistance between mm and mm is 0.003137293, and the difference between the average resistances of 10 cm and 15 cm is 0.011950234, and the difference between the average resistances of 15cm and 20cm is 0.002395406 4.

  2. Incandescent 100 watt light bulb ban: A bright Idea ?

    In halogen, the halogen gas causes a chemical reaction to take place, which removes the tungsten from the wall of the glass and deposits it back onto the filament. This extends the life of the bulb. Because this happens halogens are hotter than incandescents (Weber)

  1. Investigation of the Rubber Band as Propulsion Device

    blow dryer 6. ruler 7. thermometer 8. thermocouple 9. 50 gram weight 10. glass tube 11. paper clip 12. Nitrogen ice 13. Freezer 14. timer Method: 1. 1. Ensuring the rubber bands at room temperature are of same elasticity a) Measure the original length of the rubber band.

  2. Light Intensity Investigation

    The control variables (the variables kept the same): The other variables, which we need to keep constant, are: * The same conditions present around the experiment (room temperature, background light, disturbance, etc.). To ensure that the experiment is fair, we will minimize any background disturbance by conducting the experiment in a secluded area away from other groups.

  1. In this experiment, a mechanism is prepared to observe the refraction of light and ...

    Difference between expected value (1.334) and experimental value (1.331) is 0.003. The results of the experiment is not different from the expected value of optical density of water. In the graph of vs , the best line passes through point ?0?, that shows there is no systematic error in the experiment.

  2. Experiment to show the application of Kirchhoffs Voltage Law & Kirchhoffs Current Law in ...

    noting the direction of all the voltage drops, either positive or negative, and returning back to the same starting point. It is important to maintain the same direction either clockwise or anti-clockwise or the final voltage sum will not be equal to zero.

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