Science
(a) The power of a lens 'X' is -2·5 D. Name the lens and determine its focal length in cm. For which eye defect of vision will an optician prescribe this type of lens as a corrective lens ?
(b) "The value of magnification 'm' for a lens is -2." Using new Cartesian Sign Convention and considering that an object is placed at a distance of 20 cm from the optical centre of this lens, state :
- the nature of the image formed;
- size of the image compared to the size of the object;
- position of the image, and
- sign of the height of the image.
(c) The numerical values of the focal lengths of two lenses A and B are 10 cm and 20 cm respectively. Which one of the two will show higher degree of convergence/divergence? Give reason to justify your answer.
Related Questions
(a) Write the functions of the following parts of human female reproductive system :
- Ovary
- Fallopian tube
- Uterus
(b) State briefly two contraceptive methods used by human males.
(a) Differentiate between self-pollination and cross-pollination.
(b) Identify A, B and C in the diagram given below and write one function of each.
(a) Draw a ray diagram to show the refraction of a ray of light through a rectangular glass slab when it falls obliquely from air into glass.
(b) State Snell’s law of refraction of light.
(c) Differentiate between the virtual images formed by a convex lens and a concave lens on the basis of :
- object distance, and
- magnification
Seawater contains many salts dissolved in it. Common salt is separated from these salts. Deposits of solid salt are also found in several parts of the world. These large crystals are often brown due to impurities. This is called rock salt and is mined like coal. The common salt is an important raw material for chemicals of daily use.
(a) Write balanced chemical equations to show the products formed during electrolysis of brine.
(b) List two uses of any one product obtained during electrolysis of brine.
(c) A mild non-corrosive basic salt ‘A’, used for faster cooking, is strongly heated to produce a compound ‘B’, that is used for removing permanent hardness of water. Identify A and B and also write the equation for the reaction that occurs when A is heated.
OR
(c) Define water of crystallisation. Give two examples of salts that have water of crystallisation.