The diagram shows light incident on the centre of a semi circular glass block - Edexcel - GCSE Physics - Question 6 - 2016 - Paper 1
Question 6
The diagram shows light incident on the centre of a semi circular glass block. Angle X is less than the critical angle.
Complete the sentence by putting a cross (X)... show full transcript
Worked Solution & Example Answer:The diagram shows light incident on the centre of a semi circular glass block - Edexcel - GCSE Physics - Question 6 - 2016 - Paper 1
Step 1
Complete the sentence by putting a cross (X) in the box next to your answer.
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Answer
The ray of light emerges from the glass block along the path towards C.
Step 2
Complete the diagram to show what happens to the ray of light after it reaches the surface at point P.
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Answer
Since the angle Y is greater than the critical angle, the ray of light will undergo total internal reflection at point P.
Step 3
Explain why the light changes direction when it passes from air into the glass lens.
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Answer
The light changes direction because of refraction, which occurs when light moves from a less dense medium (air) into a more dense medium (glass). As light enters the lens, it slows down and bends towards the normal line at the interface, changing its direction.
Step 4
Calculate the power of this lens.
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Answer
The power (P) of a lens is calculated using the formula:
P = rac{1}{f}
where f is the focal length in meters.
Given that the focal length f=0.25extm, we can substitute:
P = rac{1}{0.25} = 4.0 ext{ diopters (D)}
Step 5
Discuss what is happening to the light in each example.
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Answer
In the case of the fibre optic lamp, light is guided along the fibres through total internal reflection, allowing it to travel long distances without significant loss. In the case of the plane mirror, light reflects off the surface at equal angles to its incidence, demonstrating the law of reflection.
