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.
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.
Outline a project which aims to find the dominant coat colour in dogs.
Draw the structure for the following compounds.
(i) Ethanoic acid (ii) Bromopentane*
(iii) Butanone (iv) Hexanal.
*Are structural isomers possible for bromopentane?
A hot plate of an electric oven connected to a 220 V line has two resistance coils A and B, each of 24 Ω resistance, which may be used separately, in series, or in parallel. What are the currents in the three cases?
How is the sex of the child determined in human beings?
(a) What property do all elements in the same column of the Periodic Table as boron have in common?
(b) What property do all elements in the same column of the Periodic Table as fluorine have in common?
Calculate the number of electrons constituting one coulomb of charge.
What is an homologous series? Explain with an example.
Why is variation beneficial to the species but not necessarily for the individual?
A man with blood group A marries a woman with blood group O and their daughter has blood group O. Is this information enough to tell you which of the traits – blood group A or O – is dominant? Why or why not?
The anther contains
(a) sepals.
(b) ovules.
(c) pistil.
(d) pollen grains.
By considering their position in the Periodic Table, which one of the following elements would you expect to have maximum metallic characteristic?
Ga Ge As Se Be
Why does the sky appear dark instead of blue to an astronaut?
Why does the Sun appear reddish early in the morning?
Explain why the planets do not twinkle.
Why do stars twinkle?
What happens to the image distance in the eye when we increase the distance of an object from the eye?
Why is a normal eye not able to see clearly the objects placed closer than 25 cm?
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.
The far point of a myopic person is 80 cm in front of the eye. What is the nature and power of the lens required to correct the problem?