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.

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?

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.

What is the role of the seminal vesicles and the prostate gland?

Why do you think the noble gases are placed in a separate group?

Why do HCl, HNO₃, etc., show acidic characters in aqueous solutions while solutions of compounds like alcohol and glucose do not show acidic character?

Which of the following is not a part of the female reproductive system in human beings?

(a) Ovary
(b) Uterus
(c) Vas deferens
(d) Fallopian tube

When a 12 V battery is connected across an unknown resistor, there is a current of 2.5 mA in the circuit. Find the value of the resistance of the resistor.

Why are coils of electric toasters and electric irons made of an alloy rather than a pure metal?

Let the resistance of an electrical component remains constant while the potential difference across the two ends of the component decreases to half of its former value. What change will occur in the current through it?

What is the difference between displacement and double displacement reactions? Write equations for these reactions.

The device used for producing electric current is called a

(a) generator.
(b) galvanometer.
(c) ammeter.
(d) motor.

Why are some patients of diabetes treated by giving injections of insulin?