Q22 of 30 Page 1

Draw a labelled diagram to show (i) reddish appearance of the sun at the sunrise or the sunset and (ii) white appearance of the sun at noon when it is overhead.


(i) The diagram demonstrates the reddish appearance of sun due to the phenomena of scattering of light


(ii) When the sun is nearly overhead than the light emerging from the sun undergoes less scattering compared to when the sun is at the horizon. Hence appears to be white.


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20

What are homologous structures? Give an example. Is it necessary that homologous structures always have a common ancestor. Justify your answer.

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Why is Tyndall effect shown by colloidal particles? State four instances of observing the Tyndall effect.

OR


Differentiate between a glass slab and a glass prism. What happens when a narrow beam of (i) a monochromatic light, and (ii) white light passes through


(a) Glass slab


(b) Glass prism


 23

(a) State the relation correlating the electric current flowing in a conductor and the voltage applied across it. Also draw a graph to show this relationship.

(b) Find the resistance of a conductor if the electric current flowing through it is 0.35 A when the potential difference across it is 1.4V


 24

(a) Write the mathematical expression for Joule's law of heating.

(b) Compute the heat generated while transferring 96000 coulomb of charge in two hours through a potential difference of 40 V.