NCERT Class X Science Class: Chapter – 11. Human Eye and Colourful World – Part-5 (For CBSE, ICSE, IAS, NET, NRA 2022)

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Question 16:

A student sitting at the back of the classroom cannot read clearly the letters written on the blackboard. What advice will a doctor give to her? Draw ray diagram for the correction of this defect.

Answer:

The student is suffering from myopia (near sightedness) . Doctor advises her to use a concave lens of appropriate power to correct this defect.

Question 17:

How are we able to see nearby and also the distant objects clearly?

Answer:

Human eye is able to see nearby and distant objects clearly by changing the focal length of the eye lens using its power of accommodation

Question 18:

A person needs a lens of power for correction of her vision.

(a) What kind of defect in vision is she suffering from?

(b) What is the focal length of the corrective lens?

Answer:

(a) Myopia

(b)

Question 19:

How will you use two identical prisms so that a narrow beam of white light incident on one prism emerges out of the second prism as white light? Draw the diagram.

Answer:

By using two identical prisms, one placed inverted with respect to the other we get a narrow beam of white light incident on one prism emerges out of the second prism as white light.