Case Based Questions (MCQ)

Class 10
Chapter 11 Class 10 - Human Eye and Colourful World

## Read the passage on the human eye and answer any  four questions from (a) to (e).  Eye is a natural optical device by which humans  could see objects around him. It forms an inverted,  real image on a light sensitive surface. It works on  the phenomenon of refraction of light through a  natural convex lens. However, Meena was unable to see clearly the words written on the black board  placed at a distance of approximately 3 m from her.  Her mother discussed the same with the doctor.  Doctor explained to her about this defect of vision  and its correction.

### (iv) Retina

Human eye forms the image at it’s retina.

So, the correct answer is (ii)

### (iv) Malnutrition

Given that

• Meena was unable to see clearly the words written on the black board  placed at a distance of approximately 3 m from her.
• So, she could see the  nearby objects clearly but was unable to see the far  off objects
• Thus, she was suffering from Myopia

So, the correct answer is (ii)

### (iv) None of the above

• Myopia is caused due to excessive curvature of the eye lens
• Thus, images are formed in front of the retina

So, the correct answer is (ii) - eyeball becomes long

### (iv) 25 cm

• A normal eye is not able to see   distinctly the objects placed closer than 25 cm ,  without putting any strain on the eye.
• This is  because the ciliary muscles of the eyes are unable to  contract beyond a certain limit .. Hence 25cm is the minimum focal length for the human eye.
• If the objects are  placed at a distance less than 25 cm from the eye,  then the objects appear blurred because light rays   coming from the object meet beyond the retina .

So, the correct answer is (iv) - 25 cm

### (iv) 0.85 D and – 2 D

When the far point of a person shifts from infinity to somewhere nearer, it is called nearsightedness or Myopia .

• This happens when the ciliary muscles in the eye are unable to contract further, and the lens remains thick.
• The image is formed in front of the retina instead of on it.
• This is corrected by using a diverging lens
• It increases the total focal length of the lens+eye combination, making the image on the retina.

When the near point of a person shifts from 25cm to somewhere farther,  it is called farsightedness or Hypermetropia.

• This happens when the ciliary muscles in the eye are unable to expand further, and the lens remains thin.
• The image is formed behind the retina instead of on it.
• This is corrected by using a converging lens
• It decreases the total focal length of the lens+eye combination, making the image on the retina.

Let the object distance = u

Image distance = v

Thus, the correct answer is (ii) +2D and – 1/3 D

Get live Maths 1-on-1 Classs - Class 6 to 12

#### Maninder Singh

CA Maninder Singh is a Chartered Accountant for the past 13 years and a teacher from the past 17 years. He teaches Science, Economics, Accounting and English at Teachoo