Class 10 Science - Chapter The Human Eye and the Colourful World NCERT Solutions | The human eye can focus on objects at di

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

Why do stars twinkle?

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.

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?

Why does the sky appear dark instead of blue to an astronaut?

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.

What precaution should be taken to avoid the overloading of domestic electric circuits?

At the time of short circuit, the current in the circuit

(a) reduces substantially.
(b) does not change.
(c) increases heavily.
(d) vary continuously.

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

What evidence do we have for the origin of life from inanimate matter?

Differentiate between metal and non-metal on the basis of their chemical properties.

Why is vegetative propagation practised for growing some types of plants?

Light enters from air to glass having refractive index 1.50. What is the speed of light in the glass? The speed of light in vacuum is 3 × 108 m s–1.

A solution of a substance 'X' is used for whitewashing.

   (i)  Name the substance 'X' and write its formula.
   (ii) Write the reaction of the substance 'X' named in (i) above with water.

What are the necessary conditions for autotrophic nutrition and what are its by-products?

How could the Modern Periodic Table remove various anomalies of Mendeléev’s Periodic Table?