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2004 WAEC Physics Practical   Determine and record the approximate focal length f\(_{o}\) of the concave mirror provided. Arrange...

Physics
WAEC 2004

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  1. Determine and record the approximate focal length f\(_{o}\) of the concave mirror provided.
  2. Arrange the ray box, the mirror, and the screen as shown in the diagram above.
  3. Adjust the ray box to a distance b = 20.0cm from the mirror.
  4. Adjust the position of the screen until a sharp image of the cross wire of the ray box is formed on it.
  5. Measure and record the distance, a, of the screen from the mirror. Evaluate \(\frac{a}{a}\) =1.
  6. Repeat the procedure for four other values of b = 25.0, 30.0, 35.0, and 40.0cm. Tabulate your readings.
  7. Plot a graph of l on the vertical axis against a on the horizontal axis.
  8. Determine the slope,.s, of the graph. Evaluate S\(^{-1}\).
  9. State two precautions taken to ensure accurate results.

(b)i. An object is placed at a distance of 10cm in front of a concave mirror of focal length of 15cm. Determine the characteristics of the image formed.

ii. Briefly describe how you obtained f\(_{o}\) in (a)i) above.

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Explanation

1. f\(_{o}\) = 15cm

5. a = 60.0cm, b = 20.0cm
Hence, L = \(\frac{a}{b} = \frac{60}{20}\) = 3

6. Tables of values/observation 

S/N b(cm) a(cm) L=\(\frac{a}{b}\)
1 20.0 60.00 3.00
2 25.0 37.00 1.50
3 30.0 30.00 1.00
4 35.0 26.00 0.75
5 40.0 24.00 0.6

 

7.
No description available.


8. Slope (s) = \(\frac{\bigtriangleup {L }}{\bigtriangleup {a}} = \frac{3-0.25}{60-18.6cm}\)

= \(\frac{2.75}{41.4}\) = 0.066425cm\(^{-1}\)

S\(^{-1}\) =  \(\frac{1}{s} = \frac{1}{0.066425(cm)^{-1}}\)

= 15.05 = 15

N.B: S\(^{-1}\) = f\(_{o}\) = 15cm

Precautions taken to ensure accurate results are as follows:

  1.  Parallax error in reading meter rule avoided 
  2. Readings repeated must De shown on the table
  3. Collinear alignment of apparatus ensured

(b)i. u = 10cm, f = +15cm, V= ?

\(\frac{1}{v} + \frac{1}{u} = \frac{1}{f }\)

\(\frac{1}{v} + \frac{1}{10} = \frac{1}{15}\)

\(\frac{1}{v} = \frac{1}{15} - \frac{1}{10} = \frac{2-3}{30} =\frac{1}{30}\) 

= The characteristics of the image formed are:

- it is virtual
- it is enlarged or magnified i.e twice or two times as big as the object (m = 2) 


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WAEC offline past questions - with all answers and explanations in one app - Download for free
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WAEC offline past questions - with all answers and explanations in one app - Download for free
Post-UTME Past Questions - Original materials are available here - Download PDF for your school of choice + 1 year SMS alerts
WAEC Past Questions, Objective & Theory, Study 100% offline, Download app now - 24709
WAEC May/June 2024 - Practice for Objective & Theory - From 1988 till date, download app now - 99995