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# The purpose of this laboratory investigation is to verify the validity of the Lens Equation which states that 1/di + 1/do = 1/f.

Extracts from this document...

Introduction

Lab: Applying the Lens Equation

Daniela Perdomo

Lab Partner: Stephanie Landers

Date: 21 November 2002

## Place: Graded School – São Paulo, Brazil

Time: 8:10 h – 9:35 h

Purpose/Introduction: The purpose of this laboratory investigation is to verify the validity of the Lens Equation which states that1/di + 1/do = 1/f, where di is the distance from the image to the lens, do is the distance from the object to the lens, and f is the focal length.

Hypothesis: The laboratory investigators hypothesized that the data obtained in the procedure of this experiment would be consistent with the Lens Equation. Though different methods of obtaining focal lengths (f) will be used throughout the lab, the obtained f’s should still be equal.

Materials:

• 2 double convex lenses
• 1 candle
• 1 box of matches
• 1 meter stick
• 1 lens holder
• 1 cardholder
• 1 candleholder
• 1 blank card

Diagram:

Procedure:

The first lens used in this investigation was a double convex lens, which indicates that light should converge when shone through it. The first way used to discover its focal length was by using sunlight. A cardholder, with a card in it, was placed on the meter stick and the lens holder, with the convex lens in it, placed in front of it (i.e. closer to where the sunlight was coming from).

Middle

(do)

Card distance

(di)

1/do

1/di

1/do + 1/di

(f)#

1

67.48 ± 0.1 cm

27.00 ± 0.5 cm

22.48 ± 0.2 cm

18.00 ± 0.6 cm

0.445

0.555

0.100

9.99 ± 0.4 cm

2

83.85 ± 0.1 cm

31.15 ± 0.5 cm

38.85 ± 0.2 cm

13.85 ± 0.6 cm

0.026

0.072

0.098

10.21 ± 0.5 cm

3

58.92 ± 0.1 cm

8.50 ± 0.5 cm

13.92 ± 0.2 cm

36.50 ± 0.6 cm

0.072

0.274

0.099

10.07 ± 0.9 cm

4

61.68 ± 0.1 cm

22.49 ± 0.5 cm

16.68 ± 0.2 cm

22.51 ± 0.6 cm

0.060

0.444

0.104

9.58 ± 0.4 cm

5

83.00 ± 0.1 cm

32.16 ± 0.5 cm

38.00 ± 0.2 cm

12.84 ± 0.6 cm

0.026

0.078

0.104

9.60 ± 0.6 cm

6

70.00 ± 0.1 cm

29.39 ± 0.5 cm

25.00 ± 0.2 cm

15.61 ± 0.6 cm

0.040

0.064

0.104

9.61 ± 0.4 cm

# Pleasenote: In trials 1-6 the lens was always placed at the 45.00 ± 0.

Conclusion

Suggestions: This laboratory experiment could have been improved by using optics benches instead of the flimsy metal clips and the meter stick used in this lab. Also, though it is impossible to focus on light from infinity, the investigators could have focused on something further away, such as a passing airplane. Perhaps a transparent light bulb could have been used instead and in this manner, the laboratory investigators could look at the light-producing wire, which does not shine as intermittently as candlelight does.

In addition to all of the above, some more trials could have been performed, and it would have been better to work with larger distances instead of being restrained by a meter stick, because although the same uncertainties would have been applied to the lens positions (all trials), card positions (Part A, “w/ candle”), and do(all trials), ± 0.1 cm uncertainty in a distance of, say, 5-meters would constitute a smaller margin of error than in merely a 1-meter distance.

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