Class 10 Science - Chapter The Human Eye and the Colourful World NCERT Solutions | Why is a normal eye not able to see clea

What is the far point and near point of the human eye with normal vision?

Make a diagram to show how hypermetropia is corrected. The near point of a hypermetropic eye is 1 m. What is the power of the lens required to correct this defect? Assume that the near point of the normal eye is 25 cm.

Explain why the planets do not twinkle.

Why do stars twinkle?

What is meant by power of accommodation of the eye?

The human eye forms the image of an object at its

(a) cornea.          (b) iris.          (c) pupil.          (d) retina.

A student has difficulty reading the blackboard while sitting in the last row. What could be the defect the child is suffering from? How can it be corrected?

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

(a) 25 m.          (b) 2.5 cm.          (c) 25 cm.          (d) 2.5 m.

A person with a myopic eye cannot see objects beyond 1.2 m distinctly. What should be the type of the corrective lens used to restore proper vision?

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

         (a) pupil.                        (b) retina.
         (c) ciliary muscles.        (d) iris.

Did Döbereiner’s triads also exist in the columns of Newlands’ Octaves? Compare and find out.

What is a good source of energy?

Why is diffusion insufficient to meet the oxygen requirements of multi-cellular organisms like humans?

What are trophic levels? Give an example of a food chain and state the different trophic levels in it.

What changes can you make in your habits to become more environment-friendly?

What is the difference between a reflex action and walking?

What is the importance of DNA copying in reproduction?

If a trait A exists in 10% of a population of an asexually reproducing species and a trait B exists in 60% of the same population, which trait is likely to have arisen earlier?

Why should a magnesium ribbon be cleared before burning in air?

Define the principal focus of a concave mirror.

Why is variation beneficial to the species but not necessarily for the individual?

Outline a project which aims to find the dominant coat colour in dogs.

Why is sodium kept immersed in kerosene oil?

Find the focal length of a lens of power – 2.0 D. What type of lens is this?

What determines the rate at which energy is delivered by a current?

A concave lens of focal length 15 cm forms an image 10 cm from the lens. How far is the object placed from the lens? Draw the ray diagram.

Which of the following is a plant hormone?

(a) Insulin
(b) Thyroxin
(c) Oestrogen
(d) Cytokinin.

Give the names of two energy sources that you would consider to be exhaustible. Give reasons for your choices.

A concave mirror produces three times magnified (enlarged) real image of an object placed at 10 cm in front of it. Where is the image located?

What are the two properties of carbon which lead to the huge number of carbon compounds we see around us?