Class 10 Science - Chapter The Human Eye and the Colourful World NCERT Solutions | The change in focal length of an eye len

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.

Why do stars twinkle?

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.

How does a solenoid behave like a magnet? Can you determine the north and south poles of a current–carrying solenoid with the help of a bar magnet? Explain.

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.

A positively-charged particle (alpha-particle) projected towards west is deflected towards north by a magnetic field. The direction of magnetic field is

   (a) towards south                 (b) towards east
   (c) downward                       (d) upward

Why do acids not show acidic behaviour in the absence of water?

Why is DNA copying an essential part of the process of reproduction?

Why are the small numbers of surviving tigers a cause of worry from the point of view of genetics?

Will geographical isolation be a major factor in the speciation of a self-pollinating plant species? Why or why not?

Why are traits acquired during the life-time of an individual not inherited?

What are the different ways in which individuals with a particular trait may increase in a population?

Give an example of characteristics being used to determine how close two species are in evolutionary terms.