Mock exam paper D Ordinary Level Marking Scheme

Pre-leaving Certificate Examination,

2013

Physics -Ordinary level-marking scheme

Time – 3 Hours

Answer three questions from section A and five questions from section B

Section A: (120 Marks)

Answer THREE questions from this section.

Each question carries 40 marks.

1. A student carried out an experiment to measure the focal length of a converging lens. Firstly the approximate focal length of the lens was established. Then an object was placed outside the focal length and the position of the image found by the no parallax method. The experiment was repeated for a number of values of object distance (u) and the corresponding image distance (v) found.

The results were recorded in the table below

u/cm

15.0

25.0

35.0

45.0

55.0

v/cm

60.0

23.0

18.4

16.4

15.3

Describe, with the aid of a clearly labelled diagram, how the image position was found (9)

Diagram (3)

Image pin lined up with object viewed through lens (3)

No parallax position found (3)

Indicate the distances u and v on your diagram (4)

(2x2)

Why was it necessary to first find the approximate focal length of the lens (6)

To make sure object distance greater than focal length (6)

What would happen if the object were placed inside the focal length? (6)

Image virtual – can’t find image with pin (6)

Using all of this data calculate the focal length of the lens (12)

1/f = 1/u + 1/v (at least 4 points correct) (6)

And average (6)

or intercept of graph = 1/f (12)

List two sources of error in this experiment (5)

Any two valid (3+2)

2. Draw a labelled diagram of the equipment you would use in an experiment to measure the velocity of an object (12)

Trolley, light gates//ticker tape timer, airtrack (4x3)

How would you ensure that the object is moving at constant velocity? (6)

Slight slope to compensate for gravity, airtrack (6)

State what measurements you would make in this experiment and what equipment you would use to make these measurements (12)

Length of trolley//distance travelled – metre s...

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