Class 10 Science - Chapter The Human Eye and the Colourful World NCERT Solutions | What is meant by power of accommodation

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.

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.

Why does the Sun appear reddish early in the morning?

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.

Name the substance which on treatment with chlorine yields bleaching powder.

Compare and contrast fossil fuels and the Sun as direct sources of energy.

Only variations that confer an advantage to an individual organism will survive in a population. Do you agree with this statement? Why or why not?

What are outside raw materials used for by an organism?

What type of oxides are formed when non-metals combine with oxygen?

Two lamps, one rated 100 W at 220 V, and the other 60 W at 220 V, are connected in parallel to electric mains supply. What current is drawn from the line if the supply voltage is 220 V?

Where should an object be placed in front of a convex lens to get a real image of the size of the object?

(a) At the principal focus of the lens
(b) At twice the focal length
(c) At infinity
(d) Between the optical centre of the lens and its principal focus.

A convex lens forms a real and inverted image of a needle at a distance of 50 cm from it. Where is the needle placed in front of the convex lens if the image is equal to the size of the object? Also, find the power of the lens.

Judge the equivalent resistance when the following are connected in parallel – (a) 1 Ω and 10⁶ Ω, (b) 1 Ω and 10³ Ω, and 10⁶ Ω.

What is the role of decomposers in the ecosystem?