Give two reasons why fluorspar prism is preffered over glass prism for the study of black body spectrum.

Give any four reasons why water is necessary in our body.

Give two reasons why the efficiency of a single movable pulley is not 100%.

Give reason for the following: (i) Infrared radiations are used for photography in fog. (ii) Infrared radiations are used for signals during war. (iii) The photographic darkrooms are provided with infrared lamps. (iv) A rock salt prism is used instead of a glass prism to obtain the infrared spectrum. (v) A quartz prism is required for obtaining the spectrum of ultraviolet light. (vi) Ultraviolet bulbs have a quartz envelope instead of glass.

The diagram below shows two parallel rays A and B of red and violet light respectively incident from air on air-glass boundary. Complete the diagram showing the refracted rays for them in the glass. (i) How do the speeds of the rays differ in glass ? (ii) are the two refracted rays in glass parallel ? Give a reason for your answer. (iii) How does the refractive index of glass differ for the two rays ?

In the laboratory preparation of hydrochloric acid , hydrogen chloride gas is dissolved in water . (i) Draw a diagram to show the arrangement used for the absorption of HCl gas in water. (ii) State why such an arrangement is necessary . Give two reasons for the same . (iii) Write balanced chemical equations for the laboratory preparation of HCl gas when the reactants are : A below 200^(@)C B above 200^(@)C

Giving two reasons explain why there is more species biodiversity in tropical latitudes than in temperate ones.