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Newton used a corpuscular theory of light to explain reflection - AQA - A-Level Physics - Question 2 - 2019 - Paper 7
Question 2
Newton used a corpuscular theory of light to explain reflection. Figure 2 shows how corpuscles would reflect from a horizontal surface. What happens to the horizon... show full transcript
Worked Solution & Example Answer:Newton used a corpuscular theory of light to explain reflection - AQA - A-Level Physics - Question 2 - 2019 - Paper 7
Step 1
Step 2
Discuss the evidence that led to the rejection of Newton's corpuscular theory.
Answer
Newton's corpuscular theory faced rejection due to several key factors:
Explanation of Refraction
- Newton's Theory: Newton explained refraction as a result of a change in the velocity of light as it passes from one medium to another. He presumed that the corpuscles of light would change speed which would lead to a change in direction.
- Huygens' Wave Theory: Huygens proposed that light behaves as a wave. He introduced the concept of wavefronts which describe the propagation of light and explained refraction as a bending of these wavefronts when entering a different medium.
Experimental Evidence
- Double-Slit Experiment: This experiment showed the wave nature of light through the interference patterns created by overlapping wavefronts. Such patterns could not be explained by the particle theory.
- Polarization of Light: Light was shown to have polarization properties, characteristic of waves, which further supported Huygens' wave theory over Newton’s particle theory.
- Young’s Experiment: Young’s experiment demonstrated the phenomenon of interference that could not be explained using the corpuscular theory.
Final Conclusion
Due to these observations and experimental validations, Huygens' wave theory gradually gained acceptance over Newton's corpuscular theory for explaining light behavior.
Step 3
Describe a plane-polarised electromagnetic wave travelling through a vacuum.
Answer
A plane-polarised electromagnetic wave consists of electric and magnetic fields oscillating perpendicularly to each other and to the direction of wave propagation. In a vacuum, these waves travel at the speed of light, c.
Characteristics:
- Electric Field (E): Oscillates in one plane (the plane of polarization). It is represented as an arrow at right angles to the direction of propagation.
- Magnetic Field (B): Oscillates in a plane perpendicular to the electric field.
- Both fields are perpendicular to the direction of propagation, following the right-hand rule.
Diagram (optional):
A labelled diagram can show the E and B fields, indicating their direction and highlighting their perpendicular relationship.