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?
Myopia is also known as near sightedness. A person who is suffering from this eye defect cannot see the distant objects clearly. The normal vision of the eye is 25 cm. The image is formed in front of the retina to the person who is having this defect. So, the person is advised or recommended to use concave lens of the correct power. So, the image will form on retina. Thus, this eye defect can be rectified.
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.
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.
What were the limitations of Döbereiner’s classification?
A solution reacts with crushed egg-shells to give a gas that turns lime-water milky. The solution contains
(a) NaCl (b) HCl (c) LiCl (d) KCl
The magnification produced by a plane mirror is +1. What does this mean?
Describe the structure and functioning of nephrons.
A spherical mirror and a thin spherical lens have each a focal length of –15 cm. The mirror and the lens are likely to be
(a) both concave.
(b) both convex.
(c) the mirror is concave and the lens is convex.
(d) the mirror is convex, but the lens is concave.
Why is respiration considered an exothermic reaction? Explain.
What advantage over an aquatic organism does a terrestrial organism have with regard to obtaining oxygen for respiration?
What are the necessary conditions for autotrophic nutrition and what are its by-products?
The refractive index of diamond is 2.42. What is the meaning of this statement?
What changes would you suggest in your home in order to be environment-friendly?