The Human Eye and the Colourful WorldClass 10 Physics Case Study Questions
10 Questions
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Case 1 of 10
Case Study7 marks
The Grandfather's Reading Struggle
Mr. Gupta, a 62-year-old retired teacher, enjoys reading the morning newspaper. Recently, he noticed that he has to hold the paper much farther away than he used to, almost at arm's length, to see the letters clearly. His vision for distant objects, like watching television from across the room, remains sharp. An ophthalmologist explained that this is a common age-related change. The eye's crystalline lens loses its flexibility, and the ciliary muscles, which adjust the lens's curvature, weaken over time. This reduces the eye's ability to increase the converging power of the lens sufficiently to focus on nearby objects. The doctor prescribed him a pair of reading glasses with a +2.0 D power.
Questions on this case
1(1 mark)MCQ
Which of the following defects of vision is Mr. Gupta most likely suffering from?
2(1 mark)MCQ
The doctor mentions the weakening of ciliary muscles. What is the primary function of these muscles in a healthy eye?
3(1 mark)MCQ
The prescribed glasses have a power of +2.0 D. What type of lens is this, and what is its focal length?
4(2 marks)
Explain why Mr. Gupta's near point has receded beyond the normal near point of 25 cm.
5(2 marks)
Without his glasses, where would the image of the newspaper print be formed when Mr. Gupta tries to read it at a normal distance of 25 cm? What is the role of his new glasses?
Case Study7 marks
The Backbencher's Dilemma
Rohan, a student in Class 10, always prefers to sit in the last row of the classroom. However, he has been struggling to read what the teacher writes on the blackboard. The letters appear blurry, and he often has to copy notes from his friend sitting in the front row. During a free period, he discovers that he can read his textbook perfectly, even holding it quite close to his eyes. His science teacher notices him squinting and suggests he get his eyes checked. The optometrist confirms that Rohan has a refractive error where the image of distant objects is formed in front of the retina. His far point is not at infinity but is at a distance of 4 meters from his eye.
Questions on this case
1(1 mark)MCQ
What is the name of the vision defect Rohan is suffering from?
2(1 mark)MCQ
According to the passage, what is the anatomical reason for the image of a distant object being formed in front of the retina in Rohan's eye?
3(1 mark)MCQ
What type of corrective lens should the optometrist prescribe for Rohan?
4(2 marks)
Rohan's far point is 4 meters. What does this mean in practical terms?
5(2 marks)
Calculate the power of the corrective lens Rohan needs to see distant objects clearly. (Assume the lens is worn very close to the eye).
Case Study7 marks
The Prism and the Spectrum
During a physics lab session, a group of students was given a triangular glass prism, a sheet of white paper, and a source of a narrow beam of white light. They were instructed to place the prism on the paper and allow the beam of light to fall on one of its refracting surfaces. As they slowly rotated the prism, they observed a beautiful band of colours appearing on a screen placed on the other side. The band showed a distinct sequence of colours, starting with red on the top and ending with violet at the bottom. Their teacher, Ms. Kaur, explained that the prism did not create the colours but merely separated the colours already present in the white light. She mentioned that this phenomenon is called dispersion and that different colours bend by different amounts.
Questions on this case
1(1 mark)MCQ
The phenomenon of splitting white light into its constituent colours is known as:
2(1 mark)MCQ
Based on the observation that red was on top and violet was at the bottom, which colour of light bends the most?
3(1 mark)MCQ
The band of colours observed by the students is called a:
4(2 marks)
What is the fundamental reason why different colours of light bend by different amounts when passing through the prism?
5(2 marks)
If the students were to place a second, identical prism next to the first one but in an inverted position, what would they observe on the screen beyond the second prism? Explain.