As aspirants gear up for the 71st BPSC Prelims, proficiency in Physics within the General Science syllabus is vital, as highlighted by this question from the 69th BPSC Prelims (2023) on photoelectric cells. This topic delves into the principles of modern physics, specifically the photoelectric effect, which underpins technologies like solar panels and photodetectors. Such questions align with BPSC’s focus on applied science and its relevance to India’s technological advancements, including Bihar’s push for renewable energy education. The question tests candidates’ ability to identify the function of a photoelectric cell amidst distractors, a key skill for the Prelims’ objective format.

Question and Options

Question: A photoelectric cell is a device which:
(A) Converts light energy into electric energy
(B) Converts electric energy into light energy
(C) Stores light energy
(D) None of the above

Analysis and Explanation

This question assesses candidates’ understanding of the photoelectric cell, a device rooted in the photoelectric effect, where light photons eject electrons from a material, generating an electric current. Let’s evaluate each option to determine the correct function of a photoelectric cell.

• Converts light energy into electric energy (A):
  A photoelectric cell (or photocell) is a device that generates electricity when exposed to light. It operates based on the photoelectric effect, discovered by Albert Einstein, where photons of sufficient energy strike a photosensitive material (e.g., selenium or silicon), causing electrons to be emitted. These electrons create an electric current, effectively converting light energy into electrical energy. Examples include photovoltaic cells in solar panels and photodiodes in light sensors. This description matches the primary function of a photoelectric cell.
  Evaluation: Correct, as photoelectric cells convert light energy into electric energy.
• Converts electric energy into light energy (B):
  Converting electric energy into light energy is the function of devices like light-emitting diodes (LEDs) or incandescent bulbs, where an electric current excites materials to emit photons. This is the opposite of a photoelectric cell’s function, which involves light as the input and electricity as the output.
  Evaluation: Incorrect, as this describes light-emitting devices, not photoelectric cells.
• Stores light energy (C):
  Storing light energy is not a function of photoelectric cells. While some devices, like solar thermal systems, capture light energy as heat, or batteries store electrical energy, photoelectric cells do not store energy. Instead, they convert light energy into electric energy in real-time, with no storage mechanism inherent to their operation.
  Evaluation: Incorrect, as photoelectric cells do not store energy.
• None of the above (D):
  Since option A accurately describes the function of a photoelectric cell, this option is not applicable. The photoelectric cell’s role in converting light to electricity is well-established in physics and technology.
  Evaluation: Incorrect, as option A is valid.

Key Insights:

• The photoelectric effect is the scientific basis for photoelectric cells, earning Einstein the 1921 Nobel Prize in Physics.
• Photoelectric cells are critical in renewable energy (e.g., solar power) and sensing applications (e.g., automatic lighting), relevant to India’s energy goals.
• Distractors test candidates’ ability to differentiate energy conversion processes (e.g., light-to-electric vs. electric-to-light) and avoid misconceptions about energy storage.
• The question’s moderate difficulty lies in requiring precise knowledge of the device’s function amidst plausible but incorrect alternatives.

Correct Answer

Correct Answer: (A) Converts light energy into electric energy
Reason: A photoelectric cell harnesses the photoelectric effect to convert light energy into electrical energy by generating a current when photons eject electrons from a photosensitive material. Options B, C, and D are incorrect, as they describe functions of other devices (e.g., LEDs), misconceptions (storing light), or negate the correct function.

Five Probable Questions of Similar Difficulty

To strengthen preparation for the 71st BPSC Prelims, here are five physics-related questions of comparable difficulty, focusing on energy conversion and modern physics, with concise explanations:

1. Question: What phenomenon explains the operation of a photoelectric cell?
   • (A) Electromagnetic induction
   • (B) Photoelectric effect
   • (C) Thermionic emission
   • (D) Nuclear fission
     Answer: (B) Photoelectric effect
     Explanation: The photoelectric effect, where light photons eject electrons, is the basis for photoelectric cells, unlike induction or fission.
2. Question: Which device converts electric energy into light energy?
   • (A) Solar cell
   • (B) Light-emitting diode (LED)
   • (C) Photoelectric cell
   • (D) Dynamo
     Answer: (B) Light-emitting diode (LED)
     Explanation: LEDs convert electricity to light, unlike photoelectric or solar cells, which convert light to electricity.
3. Question: In a photoelectric cell, what is the role of the photosensitive material?
   • (A) Stores light energy
   • (B) Emits electrons when struck by photons
   • (C) Converts electricity to heat
   • (D) Reflects light to a sensor
     Answer: (B) Emits electrons when struck by photons
     Explanation: Photosensitive materials (e.g., silicon) release electrons under light, generating current in photoelectric cells.
4. Question: Which application commonly uses photoelectric cells?
   • (A) Electric heating
   • (B) Solar power generation
   • (C) Sound amplification
   • (D) Magnetic storage
     Answer: (B) Solar power generation
     Explanation: Photoelectric cells, as photovoltaic cells, are integral to solar panels, converting sunlight to electricity.
5. Question: What determines the ability of light to eject electrons in a photoelectric cell?
   • (A) Light’s intensity only
   • (B) Light’s frequency and threshold energy
   • (C) Light’s color only
   • (D) Light’s speed
     Answer: (B) Light’s frequency and threshold energy
     Explanation: The photoelectric effect depends on light’s frequency exceeding the material’s threshold energy, not just intensity or color.

Key Terms Explained

• Photoelectric Cell: Device converting light energy to electric energy via the photoelectric effect (e.g., solar cells, photodiodes).
• Photoelectric Effect: Phenomenon where photons eject electrons from a material, generating electric current.
• Photosensitive Material: Substance (e.g., silicon, selenium) that emits electrons when exposed to light in photoelectric cells.
• Light Energy: Energy carried by photons, converted to electrical energy in photoelectric cells.
• Electric Energy: Energy in the form of electric current or potential, produced by photoelectric cells.
• Solar Cell: A type of photoelectric cell used in solar panels to generate electricity from sunlight.
• Photon: Quantum of light carrying energy, responsible for electron ejection in the photoelectric effect.
• Threshold Energy: Minimum energy (frequency) required for photons to eject electrons in a photoelectric material.

Preparation Strategies for 71st BPSC Prelims

To excel in physics and modern technology questions for the 71st BPSC Prelims, adopt these targeted strategies:

• Grasp Core Physics: Study the photoelectric effect, energy conversion, and device functions (e.g., photoelectric cells vs. LEDs).
• Focus on Applications: Understand real-world uses of photoelectric cells, such as solar energy, to connect theory to practice.
• Practice Conceptual Questions: Solve objective questions to differentiate between energy conversion processes and device roles.
• Revise Key Scientists: Note contributions like Einstein’s work on the photoelectric effect for historical context.
• Simulate Exam Pressure: Use timed mock tests to enhance speed and accuracy, accounting for negative marking (1/3rd per wrong answer).

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• YouTube: Access video tutorials on General Science, covering modern physics topics like the photoelectric effect.
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• Instagram/Facebook: Explore infographics and quick tips on energy conversion and device technologies.
• Website: Download mock tests, previous year papers (e.g., 69th BPSC Prelims), and comprehensive study materials.

Join Crack Target’s Dedicated BPSC Resources

Enhance your preparation with Crack Target’s tailored offerings:

• Comprehensive Notes: Study detailed materials on General Science, including optics, modern physics, and energy technologies.
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• Current Affairs Integration: Stay updated on advancements in solar technology and physics, critical for Prelims and Mains.
• Expert Support: Attend doubt-clearing sessions to clarify concepts like the photoelectric effect and device functions.

By leveraging Crack Target’s resources, aspirants can confidently tackle physics-related questions, gaining a competitive edge in the 71st BPSC Prelims. For additional 69th BPSC questions or specific topics, please share, and I’ll provide a professional response with a distinct, engaging style, as per your preference for professional language and varied presentation.