Practical Skills II: Analysis (Edexcel International A Level Physics)

A student investigated standing waves using the apparatus shown.

The signal generator was adjusted until a loud sound was heard at a particular frequency, known as the resonant frequency.

Describe how the student should use the oscilloscope to identify the resonant frequency and determine its value.

The student reduced the volume V of air inside the bottle by adding known volumes of water. He recorded the following values of the resonant frequency f for each value of V.

i) Plot a graph of log f against logV on the grid opposite. Use the additional columns in the table to record your processed data.

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ii) It is suggested that the relationship between f and V is given by

where k is a constant.

Discuss whether the graph supports this suggestion.

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A radioactive source emits beta radiation and gamma radiation.

State two precautions that should be taken when using this source.

The radiation emitted from a radioactive source can be investigated using the apparatus shown. The Geiger-Muller (GM) tube detects beta radiation and gamma radiation.

The ratemeter displays the count rate from all radiation detected by the GM tube.

Explain why the background count rate should be measured.

The corrected count rate C varies over time t according to the relationship

where C₀ is the initial count rate and λ is the decay constant.

Explain how a graph of ln C against t can be used to determine a value for λ.

The source contained two radioactive isotopes, X and Y. The table below shows the corrected count rate as the isotopes decayed.

i) Plot a graph of ln C against t on the grid opposite. Use the additional column in the table to record your processed data.

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ii) Isotope X has a half-life of approximately 30 minutes.

Determine a value of λ, in hours⁻¹, for isotope Y.

λ = .............................. hours⁻¹(3)

iii) Hence determine the half-life t_1⁄2 for isotope Y.

t_1⁄2 = ...............................

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A student used the apparatus shown to investigate the time taken for a hollow cylinder to roll down a ramp.

i) The student measured the height h₁ of the start line from the bench using a metre rule.

State two precautions she should take to ensure the measurement is as accurate as possible.

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ii) The student measured the height h₂ of the finish line. She recorded the difference in height Δh between the start line and finish line as 65 mm ± 1 mm.

Explain why the uncertainty in Δh is 1 mm.

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The student placed the cylinder on the start line and released it. She immediately started a stopwatch and measured the time t for the cylinder to roll to the finish line. She repeated the measurements several times as shown.

    i) Calculate the mean value of t and its uncertainty.

Mean value of t = ............................... ± ..........................(2)

ii) The student made the ramp less steep by reducing the value of h₁.

Explain how this might improve the measurement of t.

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Two students each carried out this procedure for another value of Δh. They recorded the following times for the same value of Δh.

Compare the accuracy and precision of the data that each student collected.

The relationship between t and the acceleration of free fall g is given by

where s is the distance along the ramp between the start line and the finish line.

The student recorded the following values.

t = 2.44 s ± 0.04 s    

s = 80.0 cm ± 0.1 cm    

Δh = 43 mm ± 1 mm

i) Determine a value for g.

g = ..............................(2)

ii) Determine the percentage uncertainty in the value of g.

Percentage uncertainty = ...........................(2)

iii) Deduce whether the value of g is accurate.

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The time period of a rotating wheel can be determined using the apparatus shown.

A magnet is attached to the edge of the wheel. When the magnet passes the coil, a single pulse is displayed on the oscilloscope screen.

The horizontal axis of the oscilloscope screen represents time. The number of milliseconds per division on the horizontal scale can be adjusted.

As the wheel rotates, a series of pulses is displayed as shown.

Describe how a value of the time period should be determined from these pulses.

When the wheel is tested, the speed of the magnet is 22.2 ms^–1.

The oscilloscope can be adjusted to give the following values for the horizontal scale.

Explain which of these scales would display two complete pulses on the screen.

wheel diameter = 25.4 cm

A student investigated the horizontal oscillations of a trolley between two springs using the apparatus shown.

The student used a stop clock to time the oscillations.

i) Describe how he should modify the equipment to make his measurements as accurate as possible.

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ii) Describe two techniques he should use to reduce the uncertainty in the value of the time period.

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The student added masses to the trolley. He measured the total mass M of the trolley and masses. He recorded the following values of the time period T for each value of M.

i) Plot a graph of log T against log M on the grid opposite. Use the additional columns in the table to record your processed data.

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ii) The student predicts that the relationship between T and M is given by

where k is the spring constant.

Discuss the validity of this prediction.

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iii) Determine the value of k.

k = .......................................................(3)

A student measured some dimensions of a thick, circular lens. The diagram shows approximate values of these dimensions.

i) The student had a set of Vernier calipers and a micrometer screw gauge, as shown in the photograph.

State, with a reason, which of these measuring instruments she should use to measure the diameter d of the lens.

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ii) The student recorded the following values of d, measured at different points across the lens.

She concluded that because her measurements were precise, they must be accurate.

Explain why this conclusion may not be justified.

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The student measured the thickness x of the edge of the lens using the micrometer screw gauge.

She recorded the following measurements.

Calculate the mean value of x in mm and its uncertainty.

Mean value of x = ............................ mm ± ........................mm

The refractive index of the material of the lens can be determined using

where f is the focal length of the lens.

i) Determine the value of .

= 5.10 cm ± 0.01 cm

= 8.30 mm ± 0.01 mm

 = 9.8 cm ± 0.3 cm

n = .......................................................(2)

ii) Show that the percentage uncertainty in is approximately 0.5 %.

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iii) Show that the uncertainty in  is approximately 0.11 cm.

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iv) The table shows data for some materials used to make lenses.

Deduce whether this lens could be made from one of these materials.

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