Advanced level 2026 Centre regional mock physics 2
Advanced level 2026 Centre regional mock physics 2
Here is the extracted data from the third image, organized by section.
Section (b): Common-Emitter Amplifier
(b) The figure below shows a simple form of a silicon common-emitter amplifier. When the collector-emitter voltage $V_{CE}$ is between $+1\text{ V}$ and $+9\text{ V}$, the collector current is about $100$ times the base current, and the base-emitter voltage $V_{BE}$ is about $0.7\text{ V}$.
Circuit Details:
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Supply Voltage: $+9\text{ V}$
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Base Resistor ($R_B$): $500\text{ k}\Omega$
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Collector Resistor ($R_C$): $3\text{ k}\Omega$
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Input: $V_i$
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Output: $V_o$
Calculate:
(i) the base current $I_B$ and the voltage $V_{CE}$ in the circuit;
(ii) the voltage gain, if the input (base-emitter) a.c. resistance is $2000\text{ }\Omega$.
(6 marks)
Section (c): Operational Amplifiers
(c) This question is based on operational amplifiers.
(i) Define the following terms as used in operational amplifiers:
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Open-loop voltage gain
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Closed-loop voltage gain.
(ii) State one effect of the feedback of the negative kind on an amplifier.
(3 marks)
Section 11 (a): Optical Fibres
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(a) A beam of light is transmitted through an optical fibre. The refractive index of the fibre’s core is $1.35$, and the refractive index of the cladding is $1.30$.
(i) Determine the critical angle for the core-cladding boundary.
(2 marks)
(ii) Explain why the angle of incidence of the beam of light should be kept at or above the critical angle.
(2 marks)
(iii) Coherent fibre bundles can be used to transmit images. Describe the main features of the structure of a coherent fibre-optic bundle, and explain why each feature is important for the bundle’s function.
(4 marks)
Section (b): Human Eye
(b) The power of unaccommodated eye is $60\text{ D}$.
(i) Calculate the image distance, $v$, when the eye focuses at infinity.
(2 marks)
(ii) The eye then focuses on an object $30\text{ cm}$ away. Calculate the extra power that the lens must produce for the eye to focus on the object.
(2 marks)
Section (c): Medical Imaging
(c) A patient is going in for a CT scan. Describe briefly how a CT scan works.
(3 marks)
