Phys Lab 2 Final

8/11/2019 Phys Lab 2 Final

1/5

Schulich School of Engineering

Physics 369: Lab 2

Thin LensesLab Section: B06

Ryan McNeil: 10134239

Shelvin Naidu: 10120389

Michael Assie: 10099639

Danny Tran: 10103598

9/30/2014


2/5

Objective:

For this laboratory we were given three experiments: measuring the focal length of various lenses

through multiple methods, constructing a compound microscope. and finally constructing a keplerian

telescope; we also take into consideration the basic concepts of paraxial approximation and the thin

lens approximation to calculate focal lengths.

Procedure:

The first experiment had three methods of attaining focal length; Using a diopter meter to record and

measure the focal length reading located on the dial when the three prongs are placed against the

surface of the lenses, and the use of the thin lens equation to calculate the focal length with

combinations of lenses (Converging and Diverging).

The second experiment was the construction of a compound microscope, this was achieved by placing

the object just a bit outside of a lens's focal length, producing an enlarged image on the screen. By

placing another lens on the opposite side of the screen where the distance between the two is just

slightly larger than the second lens's focal length and removing the screen creates a microscope effectwhen using the second lens as an eye piece.

The final experiment was the construction of a keplerian telescope, this was built by using a

combination of a long focal length lens as the objective lens, and a short focal length lens as the eye

piece. The location of the two lenses are placed such that the focal length of each coincide with each

other, just like experiment two. This combination results in a keplerian telescope where looking into the

eyepiece will produce an enlarged image of a distance object.

Data:

Experiment 1:

Method A

Figure 1: Focal Lengths Measure with Diopter Gauge

Lens Side 1 Diopter

reading [1/m]

Side 2 Diopter

Reading [1/m]

Total Diopter

Reading [1/m]

Focal Length

[m]

Focal Length

[cm]

L1 9.8 9.75 19.55 0.051150895 5.115089514

L2 4.2 4.3 8.5 0.117647059 11.76470588

L3 2.5 2.45 4.95 0.202020202 20.2020202

L4 1.25 0 1.25 0.8 80

L5 -5.26 -5.27 -10.53 -0.094966762 -9.496676163


3/5

Method B

Figure 2: Experimental Values of s and s and Calculated Focal Length for Lens L3

s (cm) s' (cm) 1/s (cm) 1/s' (cm) Focal Length (cm)

73.3 27.1 0.013642565 0.036900369 19.78515936

51.4 32.9 0.019455253 0.030395137 20.06002372

45 35.5 0.022222222 0.028169014 19.8447205

86.7 25.4 0.011534025 0.039370079 19.64478145

74.4 28 0.01344086 0.035714286 20.34375

= [1 1]

Average focal length =

Average focal length = (.7 + .7 + .7 + .7 + .7)

Average focal length = 19.936cm

Method C

Figure 3: Recorded Values and Calculated Focal Length

s (cm) b (cm) s(2)' (cm) focal Length L5 (cm) s(1)' (cm) s(2) Calculated

Focal Length40.5 37.6 4.4 -0.094966762 -0.094744599 37.6947446 3.940085106

= ()() = =

+

Experiment 2:

Figure 4: Compound Microscope Recoded Values and Calculated f(E)

s (cm) s'(0) (cm) f(0) (cm) f(E) (cm)

6.9 22.6 5.286101695 10.71389831

(0) =

() = | 1&2| (0)

Angular Magnification for the compound microscope

= (

cmS )

= (

..cm.7cm)

= 7.643


4/5

Experiment 3

Figure 5: Telescope Recoded and Calculated Values

s (cm) s' (cm) f(0) (cm) f(E) (cm)

36.3 43.9 19.86995012 5.330049875

(0) =

() = | 1&3| (0)

Angular Magnification for the Keplarian Telescope

=(

)

=(

.7.cm )

= 3.728x

Table 1: 1/s vs 1/s For L3

s

s


5/5

Focal Length of L3

=1.0160.05042 =

=

. =19.833

Discussion of L3:

Observation of the chart reveals that the y- intercept is the inverted focal length for the lens, this is

determined by using the thin lens equation:

=

by setting= 0

we attain =

therefore we can use the line of best fit's y - intercept to determine the focal length which we

calculated out to be 19.833cm. When compared to the calculated diopter reading focal length of

20.202cm and the average thin lens formula calculation of 19.936cm it can be seen that the intercept

coincides very closely but is not completely accurate. The respective percent errors were 1.83% and

0.52%.

Discussion about microscope and keplerian telescope:

The images produced from the microscope and the telescopes had magnifications of 7.633x and 3.728x

respectively. The magnifications increased the resolution of the object when viewed through the

eyepiece, where the microscope would only show part of the image, the keplerian telescope revealed

the entire image.

Documents

Phys Lab 2 Final