NCERT Class X Science Solutions: Chapter 11 – Human Eye and Colourful World Part 1

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Question 1:

The human eye can focus objects at different distances by adjusting the focal length of the eye lens. This is due to

  1. Presbyopia

  2. Accommodation

  3. Near-sightedness

  4. Far-sightedness

Answer:

B. Human eye can change the focal length of the eye lens to see the objects situated at various distances from the eye. This is possible due to the power of accommodation of the eye lens.

This diagram shows human eye can focus objects

Diagram Shows Human Eye Can Focus Objects

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Question 2:

The human eye forms the image of an object at its

  1. cornea

  2. iris

  3. pupil

  4. retina

Answer:

D. The human eye forms the image of an object at its retina.

Image result for retina

Retina

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Question 3:

The least distance of distinct vision for a young adult with normal vision is about

  1. 25 m

  2. 2.5 cm

  3. 25 cm

  4. 2.5 m

Answer:

C. The least distance of distinct vision is the minimum distance of an object to see clear and distinct image. It is 25 cm for a young adult with normal visions.

Question 4:

The change in focal length of an eye lens is caused by the action of the

  1. Pupil

  2. Retina

  3. Ciliary muscles

  4. iris

Answer:

C. The relaxation or contraction of ciliary muscles changes the curvature of the eye lens. The change in curvature of the eye lens changes the focal length of the eyes. Hence, the change in focal length of an eye lens is caused by the action of ciliary muscles.